1489 lines
91 KiB
HTML
1489 lines
91 KiB
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</head>
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<body>
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<h1 class="title toc-ignore">From base R</h1>
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<h4 class="author">Sara Stoudt</h4>
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<p>This vignette compares stringr functions to their base R equivalents
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to help users transitioning from using base R to stringr.</p>
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<div id="overall-differences" class="section level1">
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<h1>Overall differences</h1>
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<p>We’ll begin with a lookup table between the most important stringr
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functions and their base R equivalents.</p>
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<pre><code>#> Warning: There was 1 warning in `dplyr::mutate()`.
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#> ℹ In argument: `dplyr::across(.fns = ~paste0("`", .x, "`"))`.
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#> Caused by warning:
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#> ! Using `across()` without supplying `.cols` was deprecated in dplyr 1.1.0.
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#> ℹ Please supply `.cols` instead.</code></pre>
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padding-top: 8px;
|
||
padding-bottom: 8px;
|
||
padding-left: 5px;
|
||
padding-right: 5px;
|
||
color: #333333;
|
||
background-color: #FFFFFF;
|
||
font-size: 100%;
|
||
font-weight: initial;
|
||
text-transform: inherit;
|
||
border-top-style: solid;
|
||
border-top-width: 2px;
|
||
border-top-color: #D3D3D3;
|
||
border-bottom-style: solid;
|
||
border-bottom-width: 2px;
|
||
border-bottom-color: #D3D3D3;
|
||
border-left-style: none;
|
||
border-left-width: 1px;
|
||
border-left-color: #D3D3D3;
|
||
border-right-style: none;
|
||
border-right-width: 1px;
|
||
border-right-color: #D3D3D3;
|
||
vertical-align: middle;
|
||
text-align: left;
|
||
}
|
||
#kkaegzkprp .gt_empty_group_heading {
|
||
padding: 0.5px;
|
||
color: #333333;
|
||
background-color: #FFFFFF;
|
||
font-size: 100%;
|
||
font-weight: initial;
|
||
border-top-style: solid;
|
||
border-top-width: 2px;
|
||
border-top-color: #D3D3D3;
|
||
border-bottom-style: solid;
|
||
border-bottom-width: 2px;
|
||
border-bottom-color: #D3D3D3;
|
||
vertical-align: middle;
|
||
}
|
||
#kkaegzkprp .gt_from_md > :first-child {
|
||
margin-top: 0;
|
||
}
|
||
#kkaegzkprp .gt_from_md > :last-child {
|
||
margin-bottom: 0;
|
||
}
|
||
#kkaegzkprp .gt_row {
|
||
padding-top: 8px;
|
||
padding-bottom: 8px;
|
||
padding-left: 5px;
|
||
padding-right: 5px;
|
||
margin: 10px;
|
||
border-top-style: solid;
|
||
border-top-width: 1px;
|
||
border-top-color: #D3D3D3;
|
||
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|
||
border-left-width: 1px;
|
||
border-left-color: #D3D3D3;
|
||
border-right-style: none;
|
||
border-right-width: 1px;
|
||
border-right-color: #D3D3D3;
|
||
vertical-align: middle;
|
||
overflow-x: hidden;
|
||
}
|
||
#kkaegzkprp .gt_stub {
|
||
color: #333333;
|
||
background-color: #FFFFFF;
|
||
font-size: 100%;
|
||
font-weight: initial;
|
||
text-transform: inherit;
|
||
border-right-style: solid;
|
||
border-right-width: 2px;
|
||
border-right-color: #D3D3D3;
|
||
padding-left: 5px;
|
||
padding-right: 5px;
|
||
}
|
||
#kkaegzkprp .gt_stub_row_group {
|
||
color: #333333;
|
||
background-color: #FFFFFF;
|
||
font-size: 100%;
|
||
font-weight: initial;
|
||
text-transform: inherit;
|
||
border-right-style: solid;
|
||
border-right-width: 2px;
|
||
border-right-color: #D3D3D3;
|
||
padding-left: 5px;
|
||
padding-right: 5px;
|
||
vertical-align: top;
|
||
}
|
||
#kkaegzkprp .gt_row_group_first td {
|
||
border-top-width: 2px;
|
||
}
|
||
#kkaegzkprp .gt_row_group_first th {
|
||
border-top-width: 2px;
|
||
}
|
||
#kkaegzkprp .gt_summary_row {
|
||
color: #333333;
|
||
background-color: #FFFFFF;
|
||
text-transform: inherit;
|
||
padding-top: 8px;
|
||
padding-bottom: 8px;
|
||
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|
||
padding-right: 5px;
|
||
}
|
||
#kkaegzkprp .gt_first_summary_row {
|
||
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|
||
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|
||
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|
||
#kkaegzkprp .gt_first_summary_row.thick {
|
||
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|
||
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|
||
#kkaegzkprp .gt_last_summary_row {
|
||
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|
||
padding-bottom: 8px;
|
||
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|
||
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|
||
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|
||
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|
||
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|
||
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|
||
#kkaegzkprp .gt_grand_summary_row {
|
||
color: #333333;
|
||
background-color: #FFFFFF;
|
||
text-transform: inherit;
|
||
padding-top: 8px;
|
||
padding-bottom: 8px;
|
||
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|
||
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|
||
}
|
||
#kkaegzkprp .gt_first_grand_summary_row {
|
||
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|
||
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|
||
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|
||
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|
||
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|
||
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|
||
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|
||
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|
||
#kkaegzkprp .gt_last_grand_summary_row_top {
|
||
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|
||
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|
||
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|
||
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|
||
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|
||
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|
||
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|
||
}
|
||
#kkaegzkprp .gt_striped {
|
||
background-color: rgba(128, 128, 128, 0.05);
|
||
}
|
||
#kkaegzkprp .gt_table_body {
|
||
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|
||
border-top-width: 2px;
|
||
border-top-color: #D3D3D3;
|
||
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|
||
border-bottom-width: 2px;
|
||
border-bottom-color: #D3D3D3;
|
||
}
|
||
#kkaegzkprp .gt_footnotes {
|
||
color: #333333;
|
||
background-color: #FFFFFF;
|
||
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|
||
border-bottom-width: 2px;
|
||
border-bottom-color: #D3D3D3;
|
||
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|
||
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|
||
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|
||
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|
||
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|
||
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|
||
}
|
||
#kkaegzkprp .gt_footnote {
|
||
margin: 0px;
|
||
font-size: 90%;
|
||
padding-top: 4px;
|
||
padding-bottom: 4px;
|
||
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|
||
padding-right: 5px;
|
||
}
|
||
#kkaegzkprp .gt_sourcenotes {
|
||
color: #333333;
|
||
background-color: #FFFFFF;
|
||
border-bottom-style: none;
|
||
border-bottom-width: 2px;
|
||
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|
||
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|
||
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|
||
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|
||
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|
||
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|
||
border-right-color: #D3D3D3;
|
||
}
|
||
#kkaegzkprp .gt_sourcenote {
|
||
font-size: 90%;
|
||
padding-top: 4px;
|
||
padding-bottom: 4px;
|
||
padding-left: 5px;
|
||
padding-right: 5px;
|
||
}
|
||
#kkaegzkprp .gt_left {
|
||
text-align: left;
|
||
}
|
||
#kkaegzkprp .gt_center {
|
||
text-align: center;
|
||
}
|
||
#kkaegzkprp .gt_right {
|
||
text-align: right;
|
||
font-variant-numeric: tabular-nums;
|
||
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|
||
#kkaegzkprp .gt_font_normal {
|
||
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|
||
}
|
||
#kkaegzkprp .gt_font_bold {
|
||
font-weight: bold;
|
||
}
|
||
#kkaegzkprp .gt_font_italic {
|
||
font-style: italic;
|
||
}
|
||
#kkaegzkprp .gt_super {
|
||
font-size: 65%;
|
||
}
|
||
#kkaegzkprp .gt_footnote_marks {
|
||
font-size: 75%;
|
||
vertical-align: 0.4em;
|
||
position: initial;
|
||
}
|
||
#kkaegzkprp .gt_asterisk {
|
||
font-size: 100%;
|
||
vertical-align: 0;
|
||
}
|
||
#kkaegzkprp .gt_indent_1 {
|
||
text-indent: 5px;
|
||
}
|
||
#kkaegzkprp .gt_indent_2 {
|
||
text-indent: 10px;
|
||
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|
||
#kkaegzkprp .gt_indent_3 {
|
||
text-indent: 15px;
|
||
}
|
||
#kkaegzkprp .gt_indent_4 {
|
||
text-indent: 20px;
|
||
}
|
||
#kkaegzkprp .gt_indent_5 {
|
||
text-indent: 25px;
|
||
}
|
||
</style>
|
||
<table class="gt_table" data-quarto-disable-processing="false" data-quarto-bootstrap="false">
|
||
<thead>
|
||
|
||
<tr class="gt_col_headings">
|
||
<th class="gt_col_heading gt_columns_bottom_border gt_left" rowspan="1" colspan="1" scope="col" id="stringr">stringr</th>
|
||
<th class="gt_col_heading gt_columns_bottom_border gt_left" rowspan="1" colspan="1" scope="col" id="base R">base R</th>
|
||
</tr>
|
||
</thead>
|
||
<tbody class="gt_table_body">
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_detect(string, pattern)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>grepl(pattern, x)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_dup(string, times)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>strrep(x, times)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_extract(string, pattern)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>regmatches(x, m = regexpr(pattern, text))</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_extract_all(string, pattern)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>regmatches(x, m = gregexpr(pattern, text))</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_length(string)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>nchar(x)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_locate(string, pattern)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>regexpr(pattern, text)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_locate_all(string, pattern)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>gregexpr(pattern, text)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_match(string, pattern)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>regmatches(x, m = regexec(pattern, text))</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_order(string)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>order(...)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_replace(string, pattern, replacement)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>sub(pattern, replacement, x)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_replace_all(string, pattern, replacement)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>gsub(pattern, replacement, x)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_sort(string)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>sort(x)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_split(string, pattern)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>strsplit(x, split)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_sub(string, start, end)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>substr(x, start, stop)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_subset(string, pattern)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>grep(pattern, x, value = TRUE)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_to_lower(string)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>tolower(x)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_to_title(string)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>tools::toTitleCase(text)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_to_upper(string)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>toupper(x)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_trim(string)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>trimws(x)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_which(string, pattern)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>grep(pattern, x)</code></p>
|
||
</div></td></tr>
|
||
<tr><td headers="stringr" class="gt_row gt_left"><div class="gt_from_md"><p><code>str_wrap(string)</code></p>
|
||
</div></td>
|
||
<td headers="base R" class="gt_row gt_left"><div class="gt_from_md"><p><code>strwrap(x)</code></p>
|
||
</div></td></tr>
|
||
</tbody>
|
||
|
||
|
||
</table>
|
||
</div>
|
||
<p>Overall the main differences between base R and stringr are:</p>
|
||
<ol style="list-style-type: decimal">
|
||
<li><p>stringr functions start with <code>str_</code> prefix; base R
|
||
string functions have no consistent naming scheme.</p></li>
|
||
<li><p>The order of inputs is usually different between base R and
|
||
stringr. In base R, the <code>pattern</code> to match usually comes
|
||
first; in stringr, the <code>string</code> to manupulate always comes
|
||
first. This makes stringr easier to use in pipes, and with
|
||
<code>lapply()</code> or <code>purrr::map()</code>.</p></li>
|
||
<li><p>Functions in stringr tend to do less, where many of the string
|
||
processing functions in base R have multiple purposes.</p></li>
|
||
<li><p>The output and input of stringr functions has been carefully
|
||
designed. For example, the output of <code>str_locate()</code> can be
|
||
fed directly into <code>str_sub()</code>; the same is not true of
|
||
<code>regpexpr()</code> and <code>substr()</code>.</p></li>
|
||
<li><p>Base functions use arguments (like <code>perl</code>,
|
||
<code>fixed</code>, and <code>ignore.case</code>) to control how the
|
||
pattern is interpreted. To avoid dependence between arguments, stringr
|
||
instead uses helper functions (like <code>fixed()</code>,
|
||
<code>regex()</code>, and <code>coll()</code>).</p></li>
|
||
</ol>
|
||
<p>Next we’ll walk through each of the functions, noting the
|
||
similarities and important differences. These examples are adapted from
|
||
the stringr documentation and here they are contrasted with the
|
||
analogous base R operations.</p>
|
||
</div>
|
||
<div id="detect-matches" class="section level1">
|
||
<h1>Detect matches</h1>
|
||
<div id="str_detect-detect-the-presence-or-absence-of-a-pattern-in-a-string" class="section level2">
|
||
<h2><code>str_detect()</code>: Detect the presence or absence of a
|
||
pattern in a string</h2>
|
||
<p>Suppose you want to know whether each word in a vector of fruit names
|
||
contains an “a”.</p>
|
||
<div class="sourceCode" id="cb2"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb2-1"><a href="#cb2-1" tabindex="-1"></a>fruit <span class="ot"><-</span> <span class="fu">c</span>(<span class="st">"apple"</span>, <span class="st">"banana"</span>, <span class="st">"pear"</span>, <span class="st">"pineapple"</span>)</span>
|
||
<span id="cb2-2"><a href="#cb2-2" tabindex="-1"></a></span>
|
||
<span id="cb2-3"><a href="#cb2-3" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb2-4"><a href="#cb2-4" tabindex="-1"></a><span class="fu">grepl</span>(<span class="at">pattern =</span> <span class="st">"a"</span>, <span class="at">x =</span> fruit)</span>
|
||
<span id="cb2-5"><a href="#cb2-5" tabindex="-1"></a><span class="co">#> [1] TRUE TRUE TRUE TRUE</span></span>
|
||
<span id="cb2-6"><a href="#cb2-6" tabindex="-1"></a></span>
|
||
<span id="cb2-7"><a href="#cb2-7" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb2-8"><a href="#cb2-8" tabindex="-1"></a><span class="fu">str_detect</span>(fruit, <span class="at">pattern =</span> <span class="st">"a"</span>)</span>
|
||
<span id="cb2-9"><a href="#cb2-9" tabindex="-1"></a><span class="co">#> [1] TRUE TRUE TRUE TRUE</span></span></code></pre></div>
|
||
<p>In base you would use <code>grepl()</code> (see the “l” and think
|
||
logical) while in stringr you use <code>str_detect()</code> (see the
|
||
verb “detect” and think of a yes/no action).</p>
|
||
</div>
|
||
<div id="str_which-find-positions-matching-a-pattern" class="section level2">
|
||
<h2><code>str_which()</code>: Find positions matching a pattern</h2>
|
||
<p>Now you want to identify the positions of the words in a vector of
|
||
fruit names that contain an “a”.</p>
|
||
<div class="sourceCode" id="cb3"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb3-1"><a href="#cb3-1" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb3-2"><a href="#cb3-2" tabindex="-1"></a><span class="fu">grep</span>(<span class="at">pattern =</span> <span class="st">"a"</span>, <span class="at">x =</span> fruit)</span>
|
||
<span id="cb3-3"><a href="#cb3-3" tabindex="-1"></a><span class="co">#> [1] 1 2 3 4</span></span>
|
||
<span id="cb3-4"><a href="#cb3-4" tabindex="-1"></a></span>
|
||
<span id="cb3-5"><a href="#cb3-5" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb3-6"><a href="#cb3-6" tabindex="-1"></a><span class="fu">str_which</span>(fruit, <span class="at">pattern =</span> <span class="st">"a"</span>)</span>
|
||
<span id="cb3-7"><a href="#cb3-7" tabindex="-1"></a><span class="co">#> [1] 1 2 3 4</span></span></code></pre></div>
|
||
<p>In base you would use <code>grep()</code> while in stringr you use
|
||
<code>str_which()</code> (by analogy to <code>which()</code>).</p>
|
||
</div>
|
||
<div id="str_count-count-the-number-of-matches-in-a-string" class="section level2">
|
||
<h2><code>str_count()</code>: Count the number of matches in a
|
||
string</h2>
|
||
<p>How many “a”s are in each fruit?</p>
|
||
<div class="sourceCode" id="cb4"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb4-1"><a href="#cb4-1" tabindex="-1"></a><span class="co"># base </span></span>
|
||
<span id="cb4-2"><a href="#cb4-2" tabindex="-1"></a>loc <span class="ot"><-</span> <span class="fu">gregexpr</span>(<span class="at">pattern =</span> <span class="st">"a"</span>, <span class="at">text =</span> fruit, <span class="at">fixed =</span> <span class="cn">TRUE</span>)</span>
|
||
<span id="cb4-3"><a href="#cb4-3" tabindex="-1"></a><span class="fu">sapply</span>(loc, <span class="cf">function</span>(x) <span class="fu">length</span>(<span class="fu">attr</span>(x, <span class="st">"match.length"</span>)))</span>
|
||
<span id="cb4-4"><a href="#cb4-4" tabindex="-1"></a><span class="co">#> [1] 1 3 1 1</span></span>
|
||
<span id="cb4-5"><a href="#cb4-5" tabindex="-1"></a></span>
|
||
<span id="cb4-6"><a href="#cb4-6" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb4-7"><a href="#cb4-7" tabindex="-1"></a><span class="fu">str_count</span>(fruit, <span class="at">pattern =</span> <span class="st">"a"</span>)</span>
|
||
<span id="cb4-8"><a href="#cb4-8" tabindex="-1"></a><span class="co">#> [1] 1 3 1 1</span></span></code></pre></div>
|
||
<p>This information can be gleaned from <code>gregexpr()</code> in base,
|
||
but you need to look at the <code>match.length</code> attribute as the
|
||
vector uses a length-1 integer vector (<code>-1</code>) to indicate no
|
||
match.</p>
|
||
</div>
|
||
<div id="str_locate-locate-the-position-of-patterns-in-a-string" class="section level2">
|
||
<h2><code>str_locate()</code>: Locate the position of patterns in a
|
||
string</h2>
|
||
<p>Within each fruit, where does the first “p” occur? Where are all of
|
||
the “p”s?</p>
|
||
<div class="sourceCode" id="cb5"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb5-1"><a href="#cb5-1" tabindex="-1"></a>fruit3 <span class="ot"><-</span> <span class="fu">c</span>(<span class="st">"papaya"</span>, <span class="st">"lime"</span>, <span class="st">"apple"</span>)</span>
|
||
<span id="cb5-2"><a href="#cb5-2" tabindex="-1"></a></span>
|
||
<span id="cb5-3"><a href="#cb5-3" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb5-4"><a href="#cb5-4" tabindex="-1"></a><span class="fu">str</span>(<span class="fu">gregexpr</span>(<span class="at">pattern =</span> <span class="st">"p"</span>, <span class="at">text =</span> fruit3))</span>
|
||
<span id="cb5-5"><a href="#cb5-5" tabindex="-1"></a><span class="co">#> List of 3</span></span>
|
||
<span id="cb5-6"><a href="#cb5-6" tabindex="-1"></a><span class="co">#> $ : int [1:2] 1 3</span></span>
|
||
<span id="cb5-7"><a href="#cb5-7" tabindex="-1"></a><span class="co">#> ..- attr(*, "match.length")= int [1:2] 1 1</span></span>
|
||
<span id="cb5-8"><a href="#cb5-8" tabindex="-1"></a><span class="co">#> ..- attr(*, "index.type")= chr "chars"</span></span>
|
||
<span id="cb5-9"><a href="#cb5-9" tabindex="-1"></a><span class="co">#> ..- attr(*, "useBytes")= logi TRUE</span></span>
|
||
<span id="cb5-10"><a href="#cb5-10" tabindex="-1"></a><span class="co">#> $ : int -1</span></span>
|
||
<span id="cb5-11"><a href="#cb5-11" tabindex="-1"></a><span class="co">#> ..- attr(*, "match.length")= int -1</span></span>
|
||
<span id="cb5-12"><a href="#cb5-12" tabindex="-1"></a><span class="co">#> ..- attr(*, "index.type")= chr "chars"</span></span>
|
||
<span id="cb5-13"><a href="#cb5-13" tabindex="-1"></a><span class="co">#> ..- attr(*, "useBytes")= logi TRUE</span></span>
|
||
<span id="cb5-14"><a href="#cb5-14" tabindex="-1"></a><span class="co">#> $ : int [1:2] 2 3</span></span>
|
||
<span id="cb5-15"><a href="#cb5-15" tabindex="-1"></a><span class="co">#> ..- attr(*, "match.length")= int [1:2] 1 1</span></span>
|
||
<span id="cb5-16"><a href="#cb5-16" tabindex="-1"></a><span class="co">#> ..- attr(*, "index.type")= chr "chars"</span></span>
|
||
<span id="cb5-17"><a href="#cb5-17" tabindex="-1"></a><span class="co">#> ..- attr(*, "useBytes")= logi TRUE</span></span>
|
||
<span id="cb5-18"><a href="#cb5-18" tabindex="-1"></a></span>
|
||
<span id="cb5-19"><a href="#cb5-19" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb5-20"><a href="#cb5-20" tabindex="-1"></a><span class="fu">str_locate</span>(fruit3, <span class="at">pattern =</span> <span class="st">"p"</span>)</span>
|
||
<span id="cb5-21"><a href="#cb5-21" tabindex="-1"></a><span class="co">#> start end</span></span>
|
||
<span id="cb5-22"><a href="#cb5-22" tabindex="-1"></a><span class="co">#> [1,] 1 1</span></span>
|
||
<span id="cb5-23"><a href="#cb5-23" tabindex="-1"></a><span class="co">#> [2,] NA NA</span></span>
|
||
<span id="cb5-24"><a href="#cb5-24" tabindex="-1"></a><span class="co">#> [3,] 2 2</span></span>
|
||
<span id="cb5-25"><a href="#cb5-25" tabindex="-1"></a><span class="fu">str_locate_all</span>(fruit3, <span class="at">pattern =</span> <span class="st">"p"</span>)</span>
|
||
<span id="cb5-26"><a href="#cb5-26" tabindex="-1"></a><span class="co">#> [[1]]</span></span>
|
||
<span id="cb5-27"><a href="#cb5-27" tabindex="-1"></a><span class="co">#> start end</span></span>
|
||
<span id="cb5-28"><a href="#cb5-28" tabindex="-1"></a><span class="co">#> [1,] 1 1</span></span>
|
||
<span id="cb5-29"><a href="#cb5-29" tabindex="-1"></a><span class="co">#> [2,] 3 3</span></span>
|
||
<span id="cb5-30"><a href="#cb5-30" tabindex="-1"></a><span class="co">#> </span></span>
|
||
<span id="cb5-31"><a href="#cb5-31" tabindex="-1"></a><span class="co">#> [[2]]</span></span>
|
||
<span id="cb5-32"><a href="#cb5-32" tabindex="-1"></a><span class="co">#> start end</span></span>
|
||
<span id="cb5-33"><a href="#cb5-33" tabindex="-1"></a><span class="co">#> </span></span>
|
||
<span id="cb5-34"><a href="#cb5-34" tabindex="-1"></a><span class="co">#> [[3]]</span></span>
|
||
<span id="cb5-35"><a href="#cb5-35" tabindex="-1"></a><span class="co">#> start end</span></span>
|
||
<span id="cb5-36"><a href="#cb5-36" tabindex="-1"></a><span class="co">#> [1,] 2 2</span></span>
|
||
<span id="cb5-37"><a href="#cb5-37" tabindex="-1"></a><span class="co">#> [2,] 3 3</span></span></code></pre></div>
|
||
</div>
|
||
</div>
|
||
<div id="subset-strings" class="section level1">
|
||
<h1>Subset strings</h1>
|
||
<div id="str_sub-extract-and-replace-substrings-from-a-character-vector" class="section level2">
|
||
<h2><code>str_sub()</code>: Extract and replace substrings from a
|
||
character vector</h2>
|
||
<p>What if we want to grab part of a string?</p>
|
||
<div class="sourceCode" id="cb6"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb6-1"><a href="#cb6-1" tabindex="-1"></a>hw <span class="ot"><-</span> <span class="st">"Hadley Wickham"</span></span>
|
||
<span id="cb6-2"><a href="#cb6-2" tabindex="-1"></a></span>
|
||
<span id="cb6-3"><a href="#cb6-3" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb6-4"><a href="#cb6-4" tabindex="-1"></a><span class="fu">substr</span>(hw, <span class="at">start =</span> <span class="dv">1</span>, <span class="at">stop =</span> <span class="dv">6</span>)</span>
|
||
<span id="cb6-5"><a href="#cb6-5" tabindex="-1"></a><span class="co">#> [1] "Hadley"</span></span>
|
||
<span id="cb6-6"><a href="#cb6-6" tabindex="-1"></a><span class="fu">substring</span>(hw, <span class="at">first =</span> <span class="dv">1</span>) </span>
|
||
<span id="cb6-7"><a href="#cb6-7" tabindex="-1"></a><span class="co">#> [1] "Hadley Wickham"</span></span>
|
||
<span id="cb6-8"><a href="#cb6-8" tabindex="-1"></a></span>
|
||
<span id="cb6-9"><a href="#cb6-9" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb6-10"><a href="#cb6-10" tabindex="-1"></a><span class="fu">str_sub</span>(hw, <span class="at">start =</span> <span class="dv">1</span>, <span class="at">end =</span> <span class="dv">6</span>)</span>
|
||
<span id="cb6-11"><a href="#cb6-11" tabindex="-1"></a><span class="co">#> [1] "Hadley"</span></span>
|
||
<span id="cb6-12"><a href="#cb6-12" tabindex="-1"></a><span class="fu">str_sub</span>(hw, <span class="at">start =</span> <span class="dv">1</span>)</span>
|
||
<span id="cb6-13"><a href="#cb6-13" tabindex="-1"></a><span class="co">#> [1] "Hadley Wickham"</span></span>
|
||
<span id="cb6-14"><a href="#cb6-14" tabindex="-1"></a><span class="fu">str_sub</span>(hw, <span class="at">end =</span> <span class="dv">6</span>)</span>
|
||
<span id="cb6-15"><a href="#cb6-15" tabindex="-1"></a><span class="co">#> [1] "Hadley"</span></span></code></pre></div>
|
||
<p>In base you could use <code>substr()</code> or
|
||
<code>substring()</code>. The former requires both a start and stop of
|
||
the substring while the latter assumes the stop will be the end of the
|
||
string. The stringr version, <code>str_sub()</code> has the same
|
||
functionality, but also gives a default start value (the beginning of
|
||
the string). Both the base and stringr functions have the same order of
|
||
expected inputs.</p>
|
||
<p>In stringr you can use negative numbers to index from the right-hand
|
||
side string: -1 is the last letter, -2 is the second to last, and so
|
||
on.</p>
|
||
<div class="sourceCode" id="cb7"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb7-1"><a href="#cb7-1" tabindex="-1"></a><span class="fu">str_sub</span>(hw, <span class="at">start =</span> <span class="dv">1</span>, <span class="at">end =</span> <span class="sc">-</span><span class="dv">1</span>)</span>
|
||
<span id="cb7-2"><a href="#cb7-2" tabindex="-1"></a><span class="co">#> [1] "Hadley Wickham"</span></span>
|
||
<span id="cb7-3"><a href="#cb7-3" tabindex="-1"></a><span class="fu">str_sub</span>(hw, <span class="at">start =</span> <span class="sc">-</span><span class="dv">5</span>, <span class="at">end =</span> <span class="sc">-</span><span class="dv">2</span>)</span>
|
||
<span id="cb7-4"><a href="#cb7-4" tabindex="-1"></a><span class="co">#> [1] "ckha"</span></span></code></pre></div>
|
||
<p>Both base R and stringr subset are vectorized over their parameters.
|
||
This means you can either choose the same subset across multiple strings
|
||
or specify different subsets for different strings.</p>
|
||
<div class="sourceCode" id="cb8"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb8-1"><a href="#cb8-1" tabindex="-1"></a>al <span class="ot"><-</span> <span class="st">"Ada Lovelace"</span></span>
|
||
<span id="cb8-2"><a href="#cb8-2" tabindex="-1"></a></span>
|
||
<span id="cb8-3"><a href="#cb8-3" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb8-4"><a href="#cb8-4" tabindex="-1"></a><span class="fu">substr</span>(<span class="fu">c</span>(hw,al), <span class="at">start =</span> <span class="dv">1</span>, <span class="at">stop =</span> <span class="dv">6</span>)</span>
|
||
<span id="cb8-5"><a href="#cb8-5" tabindex="-1"></a><span class="co">#> [1] "Hadley" "Ada Lo"</span></span>
|
||
<span id="cb8-6"><a href="#cb8-6" tabindex="-1"></a><span class="fu">substr</span>(<span class="fu">c</span>(hw,al), <span class="at">start =</span> <span class="fu">c</span>(<span class="dv">1</span>,<span class="dv">1</span>), <span class="at">stop =</span> <span class="fu">c</span>(<span class="dv">6</span>,<span class="dv">7</span>))</span>
|
||
<span id="cb8-7"><a href="#cb8-7" tabindex="-1"></a><span class="co">#> [1] "Hadley" "Ada Lov"</span></span>
|
||
<span id="cb8-8"><a href="#cb8-8" tabindex="-1"></a></span>
|
||
<span id="cb8-9"><a href="#cb8-9" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb8-10"><a href="#cb8-10" tabindex="-1"></a><span class="fu">str_sub</span>(<span class="fu">c</span>(hw,al), <span class="at">start =</span> <span class="dv">1</span>, <span class="at">end =</span> <span class="sc">-</span><span class="dv">1</span>)</span>
|
||
<span id="cb8-11"><a href="#cb8-11" tabindex="-1"></a><span class="co">#> [1] "Hadley Wickham" "Ada Lovelace"</span></span>
|
||
<span id="cb8-12"><a href="#cb8-12" tabindex="-1"></a><span class="fu">str_sub</span>(<span class="fu">c</span>(hw,al), <span class="at">start =</span> <span class="fu">c</span>(<span class="dv">1</span>,<span class="dv">1</span>), <span class="at">end =</span> <span class="fu">c</span>(<span class="sc">-</span><span class="dv">1</span>,<span class="sc">-</span><span class="dv">2</span>))</span>
|
||
<span id="cb8-13"><a href="#cb8-13" tabindex="-1"></a><span class="co">#> [1] "Hadley Wickham" "Ada Lovelac"</span></span></code></pre></div>
|
||
<p>stringr will automatically recycle the first argument to the same
|
||
length as <code>start</code> and <code>stop</code>:</p>
|
||
<div class="sourceCode" id="cb9"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb9-1"><a href="#cb9-1" tabindex="-1"></a><span class="fu">str_sub</span>(hw, <span class="at">start =</span> <span class="dv">1</span><span class="sc">:</span><span class="dv">5</span>)</span>
|
||
<span id="cb9-2"><a href="#cb9-2" tabindex="-1"></a><span class="co">#> [1] "Hadley Wickham" "adley Wickham" "dley Wickham" "ley Wickham" </span></span>
|
||
<span id="cb9-3"><a href="#cb9-3" tabindex="-1"></a><span class="co">#> [5] "ey Wickham"</span></span></code></pre></div>
|
||
<p>Whereas the base equivalent silently uses just the first value:</p>
|
||
<div class="sourceCode" id="cb10"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb10-1"><a href="#cb10-1" tabindex="-1"></a><span class="fu">substr</span>(hw, <span class="at">start =</span> <span class="dv">1</span><span class="sc">:</span><span class="dv">5</span>, <span class="at">stop =</span> <span class="dv">15</span>)</span>
|
||
<span id="cb10-2"><a href="#cb10-2" tabindex="-1"></a><span class="co">#> [1] "Hadley Wickham"</span></span></code></pre></div>
|
||
</div>
|
||
<div id="str_sub---subset-assignment" class="section level2">
|
||
<h2><code>str_sub() <-</code>: Subset assignment</h2>
|
||
<p><code>substr()</code> behaves in a surprising way when you replace a
|
||
substring with a different number of characters:</p>
|
||
<div class="sourceCode" id="cb11"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb11-1"><a href="#cb11-1" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb11-2"><a href="#cb11-2" tabindex="-1"></a>x <span class="ot"><-</span> <span class="st">"ABCDEF"</span></span>
|
||
<span id="cb11-3"><a href="#cb11-3" tabindex="-1"></a><span class="fu">substr</span>(x, <span class="dv">1</span>, <span class="dv">3</span>) <span class="ot"><-</span> <span class="st">"x"</span></span>
|
||
<span id="cb11-4"><a href="#cb11-4" tabindex="-1"></a>x</span>
|
||
<span id="cb11-5"><a href="#cb11-5" tabindex="-1"></a><span class="co">#> [1] "xBCDEF"</span></span></code></pre></div>
|
||
<p><code>str_sub()</code> does what you would expect:</p>
|
||
<div class="sourceCode" id="cb12"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb12-1"><a href="#cb12-1" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb12-2"><a href="#cb12-2" tabindex="-1"></a>x <span class="ot"><-</span> <span class="st">"ABCDEF"</span></span>
|
||
<span id="cb12-3"><a href="#cb12-3" tabindex="-1"></a><span class="fu">str_sub</span>(x, <span class="dv">1</span>, <span class="dv">3</span>) <span class="ot"><-</span> <span class="st">"x"</span></span>
|
||
<span id="cb12-4"><a href="#cb12-4" tabindex="-1"></a>x</span>
|
||
<span id="cb12-5"><a href="#cb12-5" tabindex="-1"></a><span class="co">#> [1] "xDEF"</span></span></code></pre></div>
|
||
</div>
|
||
<div id="str_subset-keep-strings-matching-a-pattern-or-find-positions" class="section level2">
|
||
<h2><code>str_subset()</code>: Keep strings matching a pattern, or find
|
||
positions</h2>
|
||
<p>We may want to retrieve strings that contain a pattern of
|
||
interest:</p>
|
||
<div class="sourceCode" id="cb13"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb13-1"><a href="#cb13-1" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb13-2"><a href="#cb13-2" tabindex="-1"></a><span class="fu">grep</span>(<span class="at">pattern =</span> <span class="st">"g"</span>, <span class="at">x =</span> fruit, <span class="at">value =</span> <span class="cn">TRUE</span>)</span>
|
||
<span id="cb13-3"><a href="#cb13-3" tabindex="-1"></a><span class="co">#> character(0)</span></span>
|
||
<span id="cb13-4"><a href="#cb13-4" tabindex="-1"></a></span>
|
||
<span id="cb13-5"><a href="#cb13-5" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb13-6"><a href="#cb13-6" tabindex="-1"></a><span class="fu">str_subset</span>(fruit, <span class="at">pattern =</span> <span class="st">"g"</span>)</span>
|
||
<span id="cb13-7"><a href="#cb13-7" tabindex="-1"></a><span class="co">#> character(0)</span></span></code></pre></div>
|
||
</div>
|
||
<div id="str_extract-extract-matching-patterns-from-a-string" class="section level2">
|
||
<h2><code>str_extract()</code>: Extract matching patterns from a
|
||
string</h2>
|
||
<p>We may want to pick out certain patterns from a string, for example,
|
||
the digits in a shopping list:</p>
|
||
<div class="sourceCode" id="cb14"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb14-1"><a href="#cb14-1" tabindex="-1"></a>shopping_list <span class="ot"><-</span> <span class="fu">c</span>(<span class="st">"apples x4"</span>, <span class="st">"bag of flour"</span>, <span class="st">"10"</span>, <span class="st">"milk x2"</span>)</span>
|
||
<span id="cb14-2"><a href="#cb14-2" tabindex="-1"></a></span>
|
||
<span id="cb14-3"><a href="#cb14-3" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb14-4"><a href="#cb14-4" tabindex="-1"></a>matches <span class="ot"><-</span> <span class="fu">regexpr</span>(<span class="at">pattern =</span> <span class="st">"</span><span class="sc">\\</span><span class="st">d+"</span>, <span class="at">text =</span> shopping_list) <span class="co"># digits</span></span>
|
||
<span id="cb14-5"><a href="#cb14-5" tabindex="-1"></a><span class="fu">regmatches</span>(shopping_list, <span class="at">m =</span> matches)</span>
|
||
<span id="cb14-6"><a href="#cb14-6" tabindex="-1"></a><span class="co">#> [1] "4" "10" "2"</span></span>
|
||
<span id="cb14-7"><a href="#cb14-7" tabindex="-1"></a></span>
|
||
<span id="cb14-8"><a href="#cb14-8" tabindex="-1"></a>matches <span class="ot"><-</span> <span class="fu">gregexpr</span>(<span class="at">pattern =</span> <span class="st">"[a-z]+"</span>, <span class="at">text =</span> shopping_list) <span class="co"># words</span></span>
|
||
<span id="cb14-9"><a href="#cb14-9" tabindex="-1"></a><span class="fu">regmatches</span>(shopping_list, <span class="at">m =</span> matches)</span>
|
||
<span id="cb14-10"><a href="#cb14-10" tabindex="-1"></a><span class="co">#> [[1]]</span></span>
|
||
<span id="cb14-11"><a href="#cb14-11" tabindex="-1"></a><span class="co">#> [1] "apples" "x" </span></span>
|
||
<span id="cb14-12"><a href="#cb14-12" tabindex="-1"></a><span class="co">#> </span></span>
|
||
<span id="cb14-13"><a href="#cb14-13" tabindex="-1"></a><span class="co">#> [[2]]</span></span>
|
||
<span id="cb14-14"><a href="#cb14-14" tabindex="-1"></a><span class="co">#> [1] "bag" "of" "flour"</span></span>
|
||
<span id="cb14-15"><a href="#cb14-15" tabindex="-1"></a><span class="co">#> </span></span>
|
||
<span id="cb14-16"><a href="#cb14-16" tabindex="-1"></a><span class="co">#> [[3]]</span></span>
|
||
<span id="cb14-17"><a href="#cb14-17" tabindex="-1"></a><span class="co">#> character(0)</span></span>
|
||
<span id="cb14-18"><a href="#cb14-18" tabindex="-1"></a><span class="co">#> </span></span>
|
||
<span id="cb14-19"><a href="#cb14-19" tabindex="-1"></a><span class="co">#> [[4]]</span></span>
|
||
<span id="cb14-20"><a href="#cb14-20" tabindex="-1"></a><span class="co">#> [1] "milk" "x"</span></span>
|
||
<span id="cb14-21"><a href="#cb14-21" tabindex="-1"></a></span>
|
||
<span id="cb14-22"><a href="#cb14-22" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb14-23"><a href="#cb14-23" tabindex="-1"></a><span class="fu">str_extract</span>(shopping_list, <span class="at">pattern =</span> <span class="st">"</span><span class="sc">\\</span><span class="st">d+"</span>) </span>
|
||
<span id="cb14-24"><a href="#cb14-24" tabindex="-1"></a><span class="co">#> [1] "4" NA "10" "2"</span></span>
|
||
<span id="cb14-25"><a href="#cb14-25" tabindex="-1"></a><span class="fu">str_extract_all</span>(shopping_list, <span class="st">"[a-z]+"</span>)</span>
|
||
<span id="cb14-26"><a href="#cb14-26" tabindex="-1"></a><span class="co">#> [[1]]</span></span>
|
||
<span id="cb14-27"><a href="#cb14-27" tabindex="-1"></a><span class="co">#> [1] "apples" "x" </span></span>
|
||
<span id="cb14-28"><a href="#cb14-28" tabindex="-1"></a><span class="co">#> </span></span>
|
||
<span id="cb14-29"><a href="#cb14-29" tabindex="-1"></a><span class="co">#> [[2]]</span></span>
|
||
<span id="cb14-30"><a href="#cb14-30" tabindex="-1"></a><span class="co">#> [1] "bag" "of" "flour"</span></span>
|
||
<span id="cb14-31"><a href="#cb14-31" tabindex="-1"></a><span class="co">#> </span></span>
|
||
<span id="cb14-32"><a href="#cb14-32" tabindex="-1"></a><span class="co">#> [[3]]</span></span>
|
||
<span id="cb14-33"><a href="#cb14-33" tabindex="-1"></a><span class="co">#> character(0)</span></span>
|
||
<span id="cb14-34"><a href="#cb14-34" tabindex="-1"></a><span class="co">#> </span></span>
|
||
<span id="cb14-35"><a href="#cb14-35" tabindex="-1"></a><span class="co">#> [[4]]</span></span>
|
||
<span id="cb14-36"><a href="#cb14-36" tabindex="-1"></a><span class="co">#> [1] "milk" "x"</span></span></code></pre></div>
|
||
<p>Base R requires the combination of <code>regexpr()</code> with
|
||
<code>regmatches()</code>; but note that the strings without matches are
|
||
dropped from the output. stringr provides <code>str_extract()</code> and
|
||
<code>str_extract_all()</code>, and the output is always the same length
|
||
as the input.</p>
|
||
</div>
|
||
<div id="str_match-extract-matched-groups-from-a-string" class="section level2">
|
||
<h2><code>str_match()</code>: Extract matched groups from a string</h2>
|
||
<p>We may also want to extract groups from a string. Here I’m going to
|
||
use the scenario from Section 14.4.3 in <a href="https://r4ds.had.co.nz/strings.html">R for Data Science</a>.</p>
|
||
<div class="sourceCode" id="cb15"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb15-1"><a href="#cb15-1" tabindex="-1"></a><span class="fu">head</span>(sentences)</span>
|
||
<span id="cb15-2"><a href="#cb15-2" tabindex="-1"></a><span class="co">#> [1] "The birch canoe slid on the smooth planks." </span></span>
|
||
<span id="cb15-3"><a href="#cb15-3" tabindex="-1"></a><span class="co">#> [2] "Glue the sheet to the dark blue background."</span></span>
|
||
<span id="cb15-4"><a href="#cb15-4" tabindex="-1"></a><span class="co">#> [3] "It's easy to tell the depth of a well." </span></span>
|
||
<span id="cb15-5"><a href="#cb15-5" tabindex="-1"></a><span class="co">#> [4] "These days a chicken leg is a rare dish." </span></span>
|
||
<span id="cb15-6"><a href="#cb15-6" tabindex="-1"></a><span class="co">#> [5] "Rice is often served in round bowls." </span></span>
|
||
<span id="cb15-7"><a href="#cb15-7" tabindex="-1"></a><span class="co">#> [6] "The juice of lemons makes fine punch."</span></span>
|
||
<span id="cb15-8"><a href="#cb15-8" tabindex="-1"></a>noun <span class="ot"><-</span> <span class="st">"([A]a|[Tt]he) ([^ ]+)"</span></span>
|
||
<span id="cb15-9"><a href="#cb15-9" tabindex="-1"></a></span>
|
||
<span id="cb15-10"><a href="#cb15-10" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb15-11"><a href="#cb15-11" tabindex="-1"></a>matches <span class="ot"><-</span> <span class="fu">regexec</span>(<span class="at">pattern =</span> noun, <span class="at">text =</span> <span class="fu">head</span>(sentences))</span>
|
||
<span id="cb15-12"><a href="#cb15-12" tabindex="-1"></a><span class="fu">do.call</span>(<span class="st">"rbind"</span>, <span class="fu">regmatches</span>(<span class="at">x =</span> <span class="fu">head</span>(sentences), <span class="at">m =</span> matches))</span>
|
||
<span id="cb15-13"><a href="#cb15-13" tabindex="-1"></a><span class="co">#> [,1] [,2] [,3] </span></span>
|
||
<span id="cb15-14"><a href="#cb15-14" tabindex="-1"></a><span class="co">#> [1,] "The birch" "The" "birch"</span></span>
|
||
<span id="cb15-15"><a href="#cb15-15" tabindex="-1"></a><span class="co">#> [2,] "the sheet" "the" "sheet"</span></span>
|
||
<span id="cb15-16"><a href="#cb15-16" tabindex="-1"></a><span class="co">#> [3,] "the depth" "the" "depth"</span></span>
|
||
<span id="cb15-17"><a href="#cb15-17" tabindex="-1"></a><span class="co">#> [4,] "The juice" "The" "juice"</span></span>
|
||
<span id="cb15-18"><a href="#cb15-18" tabindex="-1"></a></span>
|
||
<span id="cb15-19"><a href="#cb15-19" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb15-20"><a href="#cb15-20" tabindex="-1"></a><span class="fu">str_match</span>(<span class="fu">head</span>(sentences), <span class="at">pattern =</span> noun)</span>
|
||
<span id="cb15-21"><a href="#cb15-21" tabindex="-1"></a><span class="co">#> [,1] [,2] [,3] </span></span>
|
||
<span id="cb15-22"><a href="#cb15-22" tabindex="-1"></a><span class="co">#> [1,] "The birch" "The" "birch"</span></span>
|
||
<span id="cb15-23"><a href="#cb15-23" tabindex="-1"></a><span class="co">#> [2,] "the sheet" "the" "sheet"</span></span>
|
||
<span id="cb15-24"><a href="#cb15-24" tabindex="-1"></a><span class="co">#> [3,] "the depth" "the" "depth"</span></span>
|
||
<span id="cb15-25"><a href="#cb15-25" tabindex="-1"></a><span class="co">#> [4,] NA NA NA </span></span>
|
||
<span id="cb15-26"><a href="#cb15-26" tabindex="-1"></a><span class="co">#> [5,] NA NA NA </span></span>
|
||
<span id="cb15-27"><a href="#cb15-27" tabindex="-1"></a><span class="co">#> [6,] "The juice" "The" "juice"</span></span></code></pre></div>
|
||
<p>As for extracting the full match base R requires the combination of
|
||
two functions, and inputs with no matches are dropped from the
|
||
output.</p>
|
||
</div>
|
||
</div>
|
||
<div id="manage-lengths" class="section level1">
|
||
<h1>Manage lengths</h1>
|
||
<div id="str_length-the-length-of-a-string" class="section level2">
|
||
<h2><code>str_length()</code>: The length of a string</h2>
|
||
<p>To determine the length of a string, base R uses <code>nchar()</code>
|
||
(not to be confused with <code>length()</code> which gives the length of
|
||
vectors, etc.) while stringr uses <code>str_length()</code>.</p>
|
||
<div class="sourceCode" id="cb16"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb16-1"><a href="#cb16-1" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb16-2"><a href="#cb16-2" tabindex="-1"></a><span class="fu">nchar</span>(letters)</span>
|
||
<span id="cb16-3"><a href="#cb16-3" tabindex="-1"></a><span class="co">#> [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1</span></span>
|
||
<span id="cb16-4"><a href="#cb16-4" tabindex="-1"></a></span>
|
||
<span id="cb16-5"><a href="#cb16-5" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb16-6"><a href="#cb16-6" tabindex="-1"></a><span class="fu">str_length</span>(letters)</span>
|
||
<span id="cb16-7"><a href="#cb16-7" tabindex="-1"></a><span class="co">#> [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1</span></span></code></pre></div>
|
||
<p>There are some subtle differences between base and stringr here.
|
||
<code>nchar()</code> requires a character vector, so it will return an
|
||
error if used on a factor. <code>str_length()</code> can handle a factor
|
||
input.</p>
|
||
<div class="sourceCode" id="cb17"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb17-1"><a href="#cb17-1" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb17-2"><a href="#cb17-2" tabindex="-1"></a><span class="fu">nchar</span>(<span class="fu">factor</span>(<span class="st">"abc"</span>)) </span>
|
||
<span id="cb17-3"><a href="#cb17-3" tabindex="-1"></a><span class="co">#> Error in nchar(factor("abc")): 'nchar()' requires a character vector</span></span></code></pre></div>
|
||
<div class="sourceCode" id="cb18"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb18-1"><a href="#cb18-1" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb18-2"><a href="#cb18-2" tabindex="-1"></a><span class="fu">str_length</span>(<span class="fu">factor</span>(<span class="st">"abc"</span>))</span>
|
||
<span id="cb18-3"><a href="#cb18-3" tabindex="-1"></a><span class="co">#> [1] 3</span></span></code></pre></div>
|
||
<p>Note that “characters” is a poorly defined concept, and technically
|
||
both <code>nchar()</code> and <code>str_length()</code> returns the
|
||
number of code points. This is usually the same as what you’d consider
|
||
to be a charcter, but not always:</p>
|
||
<div class="sourceCode" id="cb19"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb19-1"><a href="#cb19-1" tabindex="-1"></a>x <span class="ot"><-</span> <span class="fu">c</span>(<span class="st">"\u00fc"</span>, <span class="st">"u\u0308"</span>)</span>
|
||
<span id="cb19-2"><a href="#cb19-2" tabindex="-1"></a>x</span>
|
||
<span id="cb19-3"><a href="#cb19-3" tabindex="-1"></a><span class="co">#> [1] "ü" "ü"</span></span>
|
||
<span id="cb19-4"><a href="#cb19-4" tabindex="-1"></a></span>
|
||
<span id="cb19-5"><a href="#cb19-5" tabindex="-1"></a><span class="fu">nchar</span>(x)</span>
|
||
<span id="cb19-6"><a href="#cb19-6" tabindex="-1"></a><span class="co">#> [1] 1 2</span></span>
|
||
<span id="cb19-7"><a href="#cb19-7" tabindex="-1"></a><span class="fu">str_length</span>(x)</span>
|
||
<span id="cb19-8"><a href="#cb19-8" tabindex="-1"></a><span class="co">#> [1] 1 2</span></span></code></pre></div>
|
||
</div>
|
||
<div id="str_pad-pad-a-string" class="section level2">
|
||
<h2><code>str_pad()</code>: Pad a string</h2>
|
||
<p>To pad a string to a certain width, use stringr’s
|
||
<code>str_pad()</code>. In base R you could use <code>sprintf()</code>,
|
||
but unlike <code>str_pad()</code>, <code>sprintf()</code> has many other
|
||
functionalities.</p>
|
||
<div class="sourceCode" id="cb20"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb20-1"><a href="#cb20-1" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb20-2"><a href="#cb20-2" tabindex="-1"></a><span class="fu">sprintf</span>(<span class="st">"%30s"</span>, <span class="st">"hadley"</span>)</span>
|
||
<span id="cb20-3"><a href="#cb20-3" tabindex="-1"></a><span class="co">#> [1] " hadley"</span></span>
|
||
<span id="cb20-4"><a href="#cb20-4" tabindex="-1"></a><span class="fu">sprintf</span>(<span class="st">"%-30s"</span>, <span class="st">"hadley"</span>)</span>
|
||
<span id="cb20-5"><a href="#cb20-5" tabindex="-1"></a><span class="co">#> [1] "hadley "</span></span>
|
||
<span id="cb20-6"><a href="#cb20-6" tabindex="-1"></a><span class="co"># "both" is not as straightforward</span></span>
|
||
<span id="cb20-7"><a href="#cb20-7" tabindex="-1"></a></span>
|
||
<span id="cb20-8"><a href="#cb20-8" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb20-9"><a href="#cb20-9" tabindex="-1"></a><span class="fu">rbind</span>(</span>
|
||
<span id="cb20-10"><a href="#cb20-10" tabindex="-1"></a> <span class="fu">str_pad</span>(<span class="st">"hadley"</span>, <span class="dv">30</span>, <span class="st">"left"</span>),</span>
|
||
<span id="cb20-11"><a href="#cb20-11" tabindex="-1"></a> <span class="fu">str_pad</span>(<span class="st">"hadley"</span>, <span class="dv">30</span>, <span class="st">"right"</span>),</span>
|
||
<span id="cb20-12"><a href="#cb20-12" tabindex="-1"></a> <span class="fu">str_pad</span>(<span class="st">"hadley"</span>, <span class="dv">30</span>, <span class="st">"both"</span>)</span>
|
||
<span id="cb20-13"><a href="#cb20-13" tabindex="-1"></a>)</span>
|
||
<span id="cb20-14"><a href="#cb20-14" tabindex="-1"></a><span class="co">#> [,1] </span></span>
|
||
<span id="cb20-15"><a href="#cb20-15" tabindex="-1"></a><span class="co">#> [1,] " hadley"</span></span>
|
||
<span id="cb20-16"><a href="#cb20-16" tabindex="-1"></a><span class="co">#> [2,] "hadley "</span></span>
|
||
<span id="cb20-17"><a href="#cb20-17" tabindex="-1"></a><span class="co">#> [3,] " hadley "</span></span></code></pre></div>
|
||
</div>
|
||
<div id="str_trunc-truncate-a-character-string" class="section level2">
|
||
<h2><code>str_trunc()</code>: Truncate a character string</h2>
|
||
<p>The stringr package provides an easy way to truncate a character
|
||
string: <code>str_trunc()</code>. Base R has no function to do this
|
||
directly.</p>
|
||
<div class="sourceCode" id="cb21"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb21-1"><a href="#cb21-1" tabindex="-1"></a>x <span class="ot"><-</span> <span class="st">"This string is moderately long"</span></span>
|
||
<span id="cb21-2"><a href="#cb21-2" tabindex="-1"></a></span>
|
||
<span id="cb21-3"><a href="#cb21-3" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb21-4"><a href="#cb21-4" tabindex="-1"></a><span class="fu">rbind</span>(</span>
|
||
<span id="cb21-5"><a href="#cb21-5" tabindex="-1"></a> <span class="fu">str_trunc</span>(x, <span class="dv">20</span>, <span class="st">"right"</span>),</span>
|
||
<span id="cb21-6"><a href="#cb21-6" tabindex="-1"></a> <span class="fu">str_trunc</span>(x, <span class="dv">20</span>, <span class="st">"left"</span>),</span>
|
||
<span id="cb21-7"><a href="#cb21-7" tabindex="-1"></a> <span class="fu">str_trunc</span>(x, <span class="dv">20</span>, <span class="st">"center"</span>)</span>
|
||
<span id="cb21-8"><a href="#cb21-8" tabindex="-1"></a>)</span>
|
||
<span id="cb21-9"><a href="#cb21-9" tabindex="-1"></a><span class="co">#> [,1] </span></span>
|
||
<span id="cb21-10"><a href="#cb21-10" tabindex="-1"></a><span class="co">#> [1,] "This string is mo..."</span></span>
|
||
<span id="cb21-11"><a href="#cb21-11" tabindex="-1"></a><span class="co">#> [2,] "...s moderately long"</span></span>
|
||
<span id="cb21-12"><a href="#cb21-12" tabindex="-1"></a><span class="co">#> [3,] "This stri...ely long"</span></span></code></pre></div>
|
||
</div>
|
||
<div id="str_trim-trim-whitespace-from-a-string" class="section level2">
|
||
<h2><code>str_trim()</code>: Trim whitespace from a string</h2>
|
||
<p>Similarly, stringr provides <code>str_trim()</code> to trim
|
||
whitespace from a string. This is analogous to base R’s
|
||
<code>trimws()</code> added in R 3.3.0.</p>
|
||
<div class="sourceCode" id="cb22"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb22-1"><a href="#cb22-1" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb22-2"><a href="#cb22-2" tabindex="-1"></a><span class="fu">trimws</span>(<span class="st">" String with trailing and leading white space</span><span class="sc">\t</span><span class="st">"</span>)</span>
|
||
<span id="cb22-3"><a href="#cb22-3" tabindex="-1"></a><span class="co">#> [1] "String with trailing and leading white space"</span></span>
|
||
<span id="cb22-4"><a href="#cb22-4" tabindex="-1"></a><span class="fu">trimws</span>(<span class="st">"</span><span class="sc">\n\n</span><span class="st">String with trailing and leading white space</span><span class="sc">\n\n</span><span class="st">"</span>)</span>
|
||
<span id="cb22-5"><a href="#cb22-5" tabindex="-1"></a><span class="co">#> [1] "String with trailing and leading white space"</span></span>
|
||
<span id="cb22-6"><a href="#cb22-6" tabindex="-1"></a></span>
|
||
<span id="cb22-7"><a href="#cb22-7" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb22-8"><a href="#cb22-8" tabindex="-1"></a><span class="fu">str_trim</span>(<span class="st">" String with trailing and leading white space</span><span class="sc">\t</span><span class="st">"</span>)</span>
|
||
<span id="cb22-9"><a href="#cb22-9" tabindex="-1"></a><span class="co">#> [1] "String with trailing and leading white space"</span></span>
|
||
<span id="cb22-10"><a href="#cb22-10" tabindex="-1"></a><span class="fu">str_trim</span>(<span class="st">"</span><span class="sc">\n\n</span><span class="st">String with trailing and leading white space</span><span class="sc">\n\n</span><span class="st">"</span>)</span>
|
||
<span id="cb22-11"><a href="#cb22-11" tabindex="-1"></a><span class="co">#> [1] "String with trailing and leading white space"</span></span></code></pre></div>
|
||
<p>The stringr function <code>str_squish()</code> allows for extra
|
||
whitespace within a string to be trimmed (in contrast to
|
||
<code>str_trim()</code> which removes whitespace at the beginning and/or
|
||
end of string). In base R, one might take advantage of
|
||
<code>gsub()</code> to accomplish the same effect.</p>
|
||
<div class="sourceCode" id="cb23"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb23-1"><a href="#cb23-1" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb23-2"><a href="#cb23-2" tabindex="-1"></a><span class="fu">str_squish</span>(<span class="st">" String with trailing, middle, and leading white space</span><span class="sc">\t</span><span class="st">"</span>)</span>
|
||
<span id="cb23-3"><a href="#cb23-3" tabindex="-1"></a><span class="co">#> [1] "String with trailing, middle, and leading white space"</span></span>
|
||
<span id="cb23-4"><a href="#cb23-4" tabindex="-1"></a><span class="fu">str_squish</span>(<span class="st">"</span><span class="sc">\n\n</span><span class="st">String with excess, trailing and leading white space</span><span class="sc">\n\n</span><span class="st">"</span>)</span>
|
||
<span id="cb23-5"><a href="#cb23-5" tabindex="-1"></a><span class="co">#> [1] "String with excess, trailing and leading white space"</span></span></code></pre></div>
|
||
</div>
|
||
<div id="str_wrap-wrap-strings-into-nicely-formatted-paragraphs" class="section level2">
|
||
<h2><code>str_wrap()</code>: Wrap strings into nicely formatted
|
||
paragraphs</h2>
|
||
<p><code>strwrap()</code> and <code>str_wrap()</code> use different
|
||
algorithms. <code>str_wrap()</code> uses the famous <a href="http://litherum.blogspot.com/2015/07/knuth-plass-line-breaking-algorithm.html">Knuth-Plass
|
||
algorithm</a>.</p>
|
||
<div class="sourceCode" id="cb24"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb24-1"><a href="#cb24-1" tabindex="-1"></a>gettysburg <span class="ot"><-</span> <span class="st">"Four score and seven years ago our fathers brought forth on this continent, a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal."</span></span>
|
||
<span id="cb24-2"><a href="#cb24-2" tabindex="-1"></a></span>
|
||
<span id="cb24-3"><a href="#cb24-3" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb24-4"><a href="#cb24-4" tabindex="-1"></a><span class="fu">cat</span>(<span class="fu">strwrap</span>(gettysburg, <span class="at">width =</span> <span class="dv">60</span>), <span class="at">sep =</span> <span class="st">"</span><span class="sc">\n</span><span class="st">"</span>)</span>
|
||
<span id="cb24-5"><a href="#cb24-5" tabindex="-1"></a><span class="co">#> Four score and seven years ago our fathers brought forth on</span></span>
|
||
<span id="cb24-6"><a href="#cb24-6" tabindex="-1"></a><span class="co">#> this continent, a new nation, conceived in Liberty, and</span></span>
|
||
<span id="cb24-7"><a href="#cb24-7" tabindex="-1"></a><span class="co">#> dedicated to the proposition that all men are created</span></span>
|
||
<span id="cb24-8"><a href="#cb24-8" tabindex="-1"></a><span class="co">#> equal.</span></span>
|
||
<span id="cb24-9"><a href="#cb24-9" tabindex="-1"></a></span>
|
||
<span id="cb24-10"><a href="#cb24-10" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb24-11"><a href="#cb24-11" tabindex="-1"></a><span class="fu">cat</span>(<span class="fu">str_wrap</span>(gettysburg, <span class="at">width =</span> <span class="dv">60</span>), <span class="st">"</span><span class="sc">\n</span><span class="st">"</span>)</span>
|
||
<span id="cb24-12"><a href="#cb24-12" tabindex="-1"></a><span class="co">#> Four score and seven years ago our fathers brought forth</span></span>
|
||
<span id="cb24-13"><a href="#cb24-13" tabindex="-1"></a><span class="co">#> on this continent, a new nation, conceived in Liberty, and</span></span>
|
||
<span id="cb24-14"><a href="#cb24-14" tabindex="-1"></a><span class="co">#> dedicated to the proposition that all men are created equal.</span></span></code></pre></div>
|
||
<p>Note that <code>strwrap()</code> returns a character vector with one
|
||
element for each line; <code>str_wrap()</code> returns a single string
|
||
containing line breaks.</p>
|
||
</div>
|
||
</div>
|
||
<div id="mutate-strings" class="section level1">
|
||
<h1>Mutate strings</h1>
|
||
<div id="str_replace-replace-matched-patterns-in-a-string" class="section level2">
|
||
<h2><code>str_replace()</code>: Replace matched patterns in a
|
||
string</h2>
|
||
<p>To replace certain patterns within a string, stringr provides the
|
||
functions <code>str_replace()</code> and <code>str_replace_all()</code>.
|
||
The base R equivalents are <code>sub()</code> and <code>gsub()</code>.
|
||
Note the difference in default input order again.</p>
|
||
<div class="sourceCode" id="cb25"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb25-1"><a href="#cb25-1" tabindex="-1"></a>fruits <span class="ot"><-</span> <span class="fu">c</span>(<span class="st">"apple"</span>, <span class="st">"banana"</span>, <span class="st">"pear"</span>, <span class="st">"pineapple"</span>)</span>
|
||
<span id="cb25-2"><a href="#cb25-2" tabindex="-1"></a></span>
|
||
<span id="cb25-3"><a href="#cb25-3" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb25-4"><a href="#cb25-4" tabindex="-1"></a><span class="fu">sub</span>(<span class="st">"[aeiou]"</span>, <span class="st">"-"</span>, fruits)</span>
|
||
<span id="cb25-5"><a href="#cb25-5" tabindex="-1"></a><span class="co">#> [1] "-pple" "b-nana" "p-ar" "p-neapple"</span></span>
|
||
<span id="cb25-6"><a href="#cb25-6" tabindex="-1"></a><span class="fu">gsub</span>(<span class="st">"[aeiou]"</span>, <span class="st">"-"</span>, fruits)</span>
|
||
<span id="cb25-7"><a href="#cb25-7" tabindex="-1"></a><span class="co">#> [1] "-ppl-" "b-n-n-" "p--r" "p-n--ppl-"</span></span>
|
||
<span id="cb25-8"><a href="#cb25-8" tabindex="-1"></a></span>
|
||
<span id="cb25-9"><a href="#cb25-9" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb25-10"><a href="#cb25-10" tabindex="-1"></a><span class="fu">str_replace</span>(fruits, <span class="st">"[aeiou]"</span>, <span class="st">"-"</span>)</span>
|
||
<span id="cb25-11"><a href="#cb25-11" tabindex="-1"></a><span class="co">#> [1] "-pple" "b-nana" "p-ar" "p-neapple"</span></span>
|
||
<span id="cb25-12"><a href="#cb25-12" tabindex="-1"></a><span class="fu">str_replace_all</span>(fruits, <span class="st">"[aeiou]"</span>, <span class="st">"-"</span>)</span>
|
||
<span id="cb25-13"><a href="#cb25-13" tabindex="-1"></a><span class="co">#> [1] "-ppl-" "b-n-n-" "p--r" "p-n--ppl-"</span></span></code></pre></div>
|
||
</div>
|
||
<div id="case-convert-case-of-a-string" class="section level2">
|
||
<h2>case: Convert case of a string</h2>
|
||
<p>Both stringr and base R have functions to convert to upper and lower
|
||
case. Title case is also provided in stringr.</p>
|
||
<div class="sourceCode" id="cb26"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb26-1"><a href="#cb26-1" tabindex="-1"></a>dog <span class="ot"><-</span> <span class="st">"The quick brown dog"</span></span>
|
||
<span id="cb26-2"><a href="#cb26-2" tabindex="-1"></a></span>
|
||
<span id="cb26-3"><a href="#cb26-3" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb26-4"><a href="#cb26-4" tabindex="-1"></a><span class="fu">toupper</span>(dog)</span>
|
||
<span id="cb26-5"><a href="#cb26-5" tabindex="-1"></a><span class="co">#> [1] "THE QUICK BROWN DOG"</span></span>
|
||
<span id="cb26-6"><a href="#cb26-6" tabindex="-1"></a><span class="fu">tolower</span>(dog)</span>
|
||
<span id="cb26-7"><a href="#cb26-7" tabindex="-1"></a><span class="co">#> [1] "the quick brown dog"</span></span>
|
||
<span id="cb26-8"><a href="#cb26-8" tabindex="-1"></a>tools<span class="sc">::</span><span class="fu">toTitleCase</span>(dog)</span>
|
||
<span id="cb26-9"><a href="#cb26-9" tabindex="-1"></a><span class="co">#> [1] "The Quick Brown Dog"</span></span>
|
||
<span id="cb26-10"><a href="#cb26-10" tabindex="-1"></a></span>
|
||
<span id="cb26-11"><a href="#cb26-11" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb26-12"><a href="#cb26-12" tabindex="-1"></a><span class="fu">str_to_upper</span>(dog)</span>
|
||
<span id="cb26-13"><a href="#cb26-13" tabindex="-1"></a><span class="co">#> [1] "THE QUICK BROWN DOG"</span></span>
|
||
<span id="cb26-14"><a href="#cb26-14" tabindex="-1"></a><span class="fu">str_to_lower</span>(dog)</span>
|
||
<span id="cb26-15"><a href="#cb26-15" tabindex="-1"></a><span class="co">#> [1] "the quick brown dog"</span></span>
|
||
<span id="cb26-16"><a href="#cb26-16" tabindex="-1"></a><span class="fu">str_to_title</span>(dog)</span>
|
||
<span id="cb26-17"><a href="#cb26-17" tabindex="-1"></a><span class="co">#> [1] "The Quick Brown Dog"</span></span></code></pre></div>
|
||
<p>In stringr we can control the locale, while in base R locale
|
||
distinctions are controlled with global variables. Therefore, the output
|
||
of your base R code may vary across different computers with different
|
||
global settings.</p>
|
||
<div class="sourceCode" id="cb27"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb27-1"><a href="#cb27-1" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb27-2"><a href="#cb27-2" tabindex="-1"></a><span class="fu">str_to_upper</span>(<span class="st">"i"</span>) <span class="co"># English</span></span>
|
||
<span id="cb27-3"><a href="#cb27-3" tabindex="-1"></a><span class="co">#> [1] "I"</span></span>
|
||
<span id="cb27-4"><a href="#cb27-4" tabindex="-1"></a><span class="fu">str_to_upper</span>(<span class="st">"i"</span>, <span class="at">locale =</span> <span class="st">"tr"</span>) <span class="co"># Turkish</span></span>
|
||
<span id="cb27-5"><a href="#cb27-5" tabindex="-1"></a><span class="co">#> [1] "İ"</span></span></code></pre></div>
|
||
</div>
|
||
</div>
|
||
<div id="join-and-split" class="section level1">
|
||
<h1>Join and split</h1>
|
||
<div id="str_flatten-flatten-a-string" class="section level2">
|
||
<h2><code>str_flatten()</code>: Flatten a string</h2>
|
||
<p>If we want to take elements of a string vector and collapse them to a
|
||
single string we can use the <code>collapse</code> argument in
|
||
<code>paste()</code> or use stringr’s <code>str_flatten()</code>.</p>
|
||
<div class="sourceCode" id="cb28"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb28-1"><a href="#cb28-1" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb28-2"><a href="#cb28-2" tabindex="-1"></a><span class="fu">paste0</span>(letters, <span class="at">collapse =</span> <span class="st">"-"</span>)</span>
|
||
<span id="cb28-3"><a href="#cb28-3" tabindex="-1"></a><span class="co">#> [1] "a-b-c-d-e-f-g-h-i-j-k-l-m-n-o-p-q-r-s-t-u-v-w-x-y-z"</span></span>
|
||
<span id="cb28-4"><a href="#cb28-4" tabindex="-1"></a></span>
|
||
<span id="cb28-5"><a href="#cb28-5" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb28-6"><a href="#cb28-6" tabindex="-1"></a><span class="fu">str_flatten</span>(letters, <span class="at">collapse =</span> <span class="st">"-"</span>)</span>
|
||
<span id="cb28-7"><a href="#cb28-7" tabindex="-1"></a><span class="co">#> [1] "a-b-c-d-e-f-g-h-i-j-k-l-m-n-o-p-q-r-s-t-u-v-w-x-y-z"</span></span></code></pre></div>
|
||
<p>The advantage of <code>str_flatten()</code> is that it always returns
|
||
a vector the same length as its input; to predict the return length of
|
||
<code>paste()</code> you must carefully read all arguments.</p>
|
||
</div>
|
||
<div id="str_dup-duplicate-strings-within-a-character-vector" class="section level2">
|
||
<h2><code>str_dup()</code>: duplicate strings within a character
|
||
vector</h2>
|
||
<p>To duplicate strings within a character vector use
|
||
<code>strrep()</code> (in R 3.3.0 or greater) or
|
||
<code>str_dup()</code>:</p>
|
||
<div class="sourceCode" id="cb29"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb29-1"><a href="#cb29-1" tabindex="-1"></a>fruit <span class="ot"><-</span> <span class="fu">c</span>(<span class="st">"apple"</span>, <span class="st">"pear"</span>, <span class="st">"banana"</span>)</span>
|
||
<span id="cb29-2"><a href="#cb29-2" tabindex="-1"></a></span>
|
||
<span id="cb29-3"><a href="#cb29-3" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb29-4"><a href="#cb29-4" tabindex="-1"></a><span class="fu">strrep</span>(fruit, <span class="dv">2</span>)</span>
|
||
<span id="cb29-5"><a href="#cb29-5" tabindex="-1"></a><span class="co">#> [1] "appleapple" "pearpear" "bananabanana"</span></span>
|
||
<span id="cb29-6"><a href="#cb29-6" tabindex="-1"></a><span class="fu">strrep</span>(fruit, <span class="dv">1</span><span class="sc">:</span><span class="dv">3</span>)</span>
|
||
<span id="cb29-7"><a href="#cb29-7" tabindex="-1"></a><span class="co">#> [1] "apple" "pearpear" "bananabananabanana"</span></span>
|
||
<span id="cb29-8"><a href="#cb29-8" tabindex="-1"></a></span>
|
||
<span id="cb29-9"><a href="#cb29-9" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb29-10"><a href="#cb29-10" tabindex="-1"></a><span class="fu">str_dup</span>(fruit, <span class="dv">2</span>)</span>
|
||
<span id="cb29-11"><a href="#cb29-11" tabindex="-1"></a><span class="co">#> [1] "appleapple" "pearpear" "bananabanana"</span></span>
|
||
<span id="cb29-12"><a href="#cb29-12" tabindex="-1"></a><span class="fu">str_dup</span>(fruit, <span class="dv">1</span><span class="sc">:</span><span class="dv">3</span>)</span>
|
||
<span id="cb29-13"><a href="#cb29-13" tabindex="-1"></a><span class="co">#> [1] "apple" "pearpear" "bananabananabanana"</span></span></code></pre></div>
|
||
</div>
|
||
<div id="str_split-split-up-a-string-into-pieces" class="section level2">
|
||
<h2><code>str_split()</code>: Split up a string into pieces</h2>
|
||
<p>To split a string into pieces with breaks based on a particular
|
||
pattern match stringr uses <code>str_split()</code> and base R uses
|
||
<code>strsplit()</code>. Unlike most other functions,
|
||
<code>strsplit()</code> starts with the character vector to modify.</p>
|
||
<div class="sourceCode" id="cb30"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb30-1"><a href="#cb30-1" tabindex="-1"></a>fruits <span class="ot"><-</span> <span class="fu">c</span>(</span>
|
||
<span id="cb30-2"><a href="#cb30-2" tabindex="-1"></a> <span class="st">"apples and oranges and pears and bananas"</span>,</span>
|
||
<span id="cb30-3"><a href="#cb30-3" tabindex="-1"></a> <span class="st">"pineapples and mangos and guavas"</span></span>
|
||
<span id="cb30-4"><a href="#cb30-4" tabindex="-1"></a>)</span>
|
||
<span id="cb30-5"><a href="#cb30-5" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb30-6"><a href="#cb30-6" tabindex="-1"></a><span class="fu">strsplit</span>(fruits, <span class="st">" and "</span>)</span>
|
||
<span id="cb30-7"><a href="#cb30-7" tabindex="-1"></a><span class="co">#> [[1]]</span></span>
|
||
<span id="cb30-8"><a href="#cb30-8" tabindex="-1"></a><span class="co">#> [1] "apples" "oranges" "pears" "bananas"</span></span>
|
||
<span id="cb30-9"><a href="#cb30-9" tabindex="-1"></a><span class="co">#> </span></span>
|
||
<span id="cb30-10"><a href="#cb30-10" tabindex="-1"></a><span class="co">#> [[2]]</span></span>
|
||
<span id="cb30-11"><a href="#cb30-11" tabindex="-1"></a><span class="co">#> [1] "pineapples" "mangos" "guavas"</span></span>
|
||
<span id="cb30-12"><a href="#cb30-12" tabindex="-1"></a></span>
|
||
<span id="cb30-13"><a href="#cb30-13" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb30-14"><a href="#cb30-14" tabindex="-1"></a><span class="fu">str_split</span>(fruits, <span class="st">" and "</span>)</span>
|
||
<span id="cb30-15"><a href="#cb30-15" tabindex="-1"></a><span class="co">#> [[1]]</span></span>
|
||
<span id="cb30-16"><a href="#cb30-16" tabindex="-1"></a><span class="co">#> [1] "apples" "oranges" "pears" "bananas"</span></span>
|
||
<span id="cb30-17"><a href="#cb30-17" tabindex="-1"></a><span class="co">#> </span></span>
|
||
<span id="cb30-18"><a href="#cb30-18" tabindex="-1"></a><span class="co">#> [[2]]</span></span>
|
||
<span id="cb30-19"><a href="#cb30-19" tabindex="-1"></a><span class="co">#> [1] "pineapples" "mangos" "guavas"</span></span></code></pre></div>
|
||
<p>The stringr package’s <code>str_split()</code> allows for more
|
||
control over the split, including restricting the number of possible
|
||
matches.</p>
|
||
<div class="sourceCode" id="cb31"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb31-1"><a href="#cb31-1" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb31-2"><a href="#cb31-2" tabindex="-1"></a><span class="fu">str_split</span>(fruits, <span class="st">" and "</span>, <span class="at">n =</span> <span class="dv">3</span>)</span>
|
||
<span id="cb31-3"><a href="#cb31-3" tabindex="-1"></a><span class="co">#> [[1]]</span></span>
|
||
<span id="cb31-4"><a href="#cb31-4" tabindex="-1"></a><span class="co">#> [1] "apples" "oranges" "pears and bananas"</span></span>
|
||
<span id="cb31-5"><a href="#cb31-5" tabindex="-1"></a><span class="co">#> </span></span>
|
||
<span id="cb31-6"><a href="#cb31-6" tabindex="-1"></a><span class="co">#> [[2]]</span></span>
|
||
<span id="cb31-7"><a href="#cb31-7" tabindex="-1"></a><span class="co">#> [1] "pineapples" "mangos" "guavas"</span></span>
|
||
<span id="cb31-8"><a href="#cb31-8" tabindex="-1"></a><span class="fu">str_split</span>(fruits, <span class="st">" and "</span>, <span class="at">n =</span> <span class="dv">2</span>)</span>
|
||
<span id="cb31-9"><a href="#cb31-9" tabindex="-1"></a><span class="co">#> [[1]]</span></span>
|
||
<span id="cb31-10"><a href="#cb31-10" tabindex="-1"></a><span class="co">#> [1] "apples" "oranges and pears and bananas"</span></span>
|
||
<span id="cb31-11"><a href="#cb31-11" tabindex="-1"></a><span class="co">#> </span></span>
|
||
<span id="cb31-12"><a href="#cb31-12" tabindex="-1"></a><span class="co">#> [[2]]</span></span>
|
||
<span id="cb31-13"><a href="#cb31-13" tabindex="-1"></a><span class="co">#> [1] "pineapples" "mangos and guavas"</span></span></code></pre></div>
|
||
</div>
|
||
<div id="str_glue-interpolate-strings" class="section level2">
|
||
<h2><code>str_glue()</code>: Interpolate strings</h2>
|
||
<p>It’s often useful to interpolate varying values into a fixed string.
|
||
In base R, you can use <code>sprintf()</code> for this purpose; stringr
|
||
provides a wrapper for the more general purpose <a href="https://glue.tidyverse.org">glue</a> package.</p>
|
||
<div class="sourceCode" id="cb32"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb32-1"><a href="#cb32-1" tabindex="-1"></a>name <span class="ot"><-</span> <span class="st">"Fred"</span></span>
|
||
<span id="cb32-2"><a href="#cb32-2" tabindex="-1"></a>age <span class="ot"><-</span> <span class="dv">50</span></span>
|
||
<span id="cb32-3"><a href="#cb32-3" tabindex="-1"></a>anniversary <span class="ot"><-</span> <span class="fu">as.Date</span>(<span class="st">"1991-10-12"</span>)</span>
|
||
<span id="cb32-4"><a href="#cb32-4" tabindex="-1"></a></span>
|
||
<span id="cb32-5"><a href="#cb32-5" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb32-6"><a href="#cb32-6" tabindex="-1"></a><span class="fu">sprintf</span>(</span>
|
||
<span id="cb32-7"><a href="#cb32-7" tabindex="-1"></a> <span class="st">"My name is %s my age next year is %s and my anniversary is %s."</span>, </span>
|
||
<span id="cb32-8"><a href="#cb32-8" tabindex="-1"></a> name,</span>
|
||
<span id="cb32-9"><a href="#cb32-9" tabindex="-1"></a> age <span class="sc">+</span> <span class="dv">1</span>,</span>
|
||
<span id="cb32-10"><a href="#cb32-10" tabindex="-1"></a> <span class="fu">format</span>(anniversary, <span class="st">"%A, %B %d, %Y"</span>)</span>
|
||
<span id="cb32-11"><a href="#cb32-11" tabindex="-1"></a>)</span>
|
||
<span id="cb32-12"><a href="#cb32-12" tabindex="-1"></a><span class="co">#> [1] "My name is Fred my age next year is 51 and my anniversary is Saturday, October 12, 1991."</span></span>
|
||
<span id="cb32-13"><a href="#cb32-13" tabindex="-1"></a></span>
|
||
<span id="cb32-14"><a href="#cb32-14" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb32-15"><a href="#cb32-15" tabindex="-1"></a><span class="fu">str_glue</span>(</span>
|
||
<span id="cb32-16"><a href="#cb32-16" tabindex="-1"></a> <span class="st">"My name is {name}, "</span>,</span>
|
||
<span id="cb32-17"><a href="#cb32-17" tabindex="-1"></a> <span class="st">"my age next year is {age + 1}, "</span>,</span>
|
||
<span id="cb32-18"><a href="#cb32-18" tabindex="-1"></a> <span class="st">"and my anniversary is {format(anniversary, '%A, %B %d, %Y')}."</span></span>
|
||
<span id="cb32-19"><a href="#cb32-19" tabindex="-1"></a>)</span>
|
||
<span id="cb32-20"><a href="#cb32-20" tabindex="-1"></a><span class="co">#> My name is Fred, my age next year is 51, and my anniversary is Saturday, October 12, 1991.</span></span></code></pre></div>
|
||
</div>
|
||
</div>
|
||
<div id="order-strings" class="section level1">
|
||
<h1>Order strings</h1>
|
||
<div id="str_order-order-or-sort-a-character-vector" class="section level2">
|
||
<h2><code>str_order()</code>: Order or sort a character vector</h2>
|
||
<p>Both base R and stringr have separate functions to order and sort
|
||
strings.</p>
|
||
<div class="sourceCode" id="cb33"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb33-1"><a href="#cb33-1" tabindex="-1"></a><span class="co"># base</span></span>
|
||
<span id="cb33-2"><a href="#cb33-2" tabindex="-1"></a><span class="fu">order</span>(letters)</span>
|
||
<span id="cb33-3"><a href="#cb33-3" tabindex="-1"></a><span class="co">#> [1] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25</span></span>
|
||
<span id="cb33-4"><a href="#cb33-4" tabindex="-1"></a><span class="co">#> [26] 26</span></span>
|
||
<span id="cb33-5"><a href="#cb33-5" tabindex="-1"></a><span class="fu">sort</span>(letters)</span>
|
||
<span id="cb33-6"><a href="#cb33-6" tabindex="-1"></a><span class="co">#> [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s"</span></span>
|
||
<span id="cb33-7"><a href="#cb33-7" tabindex="-1"></a><span class="co">#> [20] "t" "u" "v" "w" "x" "y" "z"</span></span>
|
||
<span id="cb33-8"><a href="#cb33-8" tabindex="-1"></a></span>
|
||
<span id="cb33-9"><a href="#cb33-9" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb33-10"><a href="#cb33-10" tabindex="-1"></a><span class="fu">str_order</span>(letters)</span>
|
||
<span id="cb33-11"><a href="#cb33-11" tabindex="-1"></a><span class="co">#> [1] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25</span></span>
|
||
<span id="cb33-12"><a href="#cb33-12" tabindex="-1"></a><span class="co">#> [26] 26</span></span>
|
||
<span id="cb33-13"><a href="#cb33-13" tabindex="-1"></a><span class="fu">str_sort</span>(letters)</span>
|
||
<span id="cb33-14"><a href="#cb33-14" tabindex="-1"></a><span class="co">#> [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s"</span></span>
|
||
<span id="cb33-15"><a href="#cb33-15" tabindex="-1"></a><span class="co">#> [20] "t" "u" "v" "w" "x" "y" "z"</span></span></code></pre></div>
|
||
<p>Some options in <code>str_order()</code> and <code>str_sort()</code>
|
||
don’t have analogous base R options. For example, the stringr functions
|
||
have a <code>locale</code> argument to control how to order or sort. In
|
||
base R the locale is a global setting, so the outputs of
|
||
<code>sort()</code> and <code>order()</code> may differ across different
|
||
computers. For example, in the Norwegian alphabet, å comes after z:</p>
|
||
<div class="sourceCode" id="cb34"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb34-1"><a href="#cb34-1" tabindex="-1"></a>x <span class="ot"><-</span> <span class="fu">c</span>(<span class="st">"å"</span>, <span class="st">"a"</span>, <span class="st">"z"</span>)</span>
|
||
<span id="cb34-2"><a href="#cb34-2" tabindex="-1"></a><span class="fu">str_sort</span>(x)</span>
|
||
<span id="cb34-3"><a href="#cb34-3" tabindex="-1"></a><span class="co">#> [1] "a" "å" "z"</span></span>
|
||
<span id="cb34-4"><a href="#cb34-4" tabindex="-1"></a><span class="fu">str_sort</span>(x, <span class="at">locale =</span> <span class="st">"no"</span>)</span>
|
||
<span id="cb34-5"><a href="#cb34-5" tabindex="-1"></a><span class="co">#> [1] "a" "z" "å"</span></span></code></pre></div>
|
||
<p>The stringr functions also have a <code>numeric</code> argument to
|
||
sort digits numerically instead of treating them as strings.</p>
|
||
<div class="sourceCode" id="cb35"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb35-1"><a href="#cb35-1" tabindex="-1"></a><span class="co"># stringr</span></span>
|
||
<span id="cb35-2"><a href="#cb35-2" tabindex="-1"></a>x <span class="ot"><-</span> <span class="fu">c</span>(<span class="st">"100a10"</span>, <span class="st">"100a5"</span>, <span class="st">"2b"</span>, <span class="st">"2a"</span>)</span>
|
||
<span id="cb35-3"><a href="#cb35-3" tabindex="-1"></a><span class="fu">str_sort</span>(x)</span>
|
||
<span id="cb35-4"><a href="#cb35-4" tabindex="-1"></a><span class="co">#> [1] "100a10" "100a5" "2a" "2b"</span></span>
|
||
<span id="cb35-5"><a href="#cb35-5" tabindex="-1"></a><span class="fu">str_sort</span>(x, <span class="at">numeric =</span> <span class="cn">TRUE</span>)</span>
|
||
<span id="cb35-6"><a href="#cb35-6" tabindex="-1"></a><span class="co">#> [1] "2a" "2b" "100a5" "100a10"</span></span></code></pre></div>
|
||
</div>
|
||
</div>
|
||
|
||
|
||
|
||
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