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</head>
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<body>
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<h1 class="title toc-ignore">Extending tibble</h1>
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<h4 class="author">Kirill Müller, Hadley Wickham</h4>
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<p>Tibbles are S3 objects of class
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<code>c("tbl_df", "tbl", "data.frame")</code>. This means that they
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inherit their behavior from the <code>"data.frame"</code> class and add
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two subclasses <code>"tbl"</code> and <code>"tbl_df"</code>. The pillar
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and tibble packages provide methods for <code>"tbl"</code> and
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<code>"tbl_df"</code>, respectively. Package authors and programmers can
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implement subclasses that extend either <code>"tbl_df"</code> (and its
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subclasses) or only <code>"tbl"</code> to provide custom behavior for
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tibble-like objects. In addition, vectors classes can be implemented
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from scratch or on top of existing classes, to be used as columns. This
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article provides links to the various customization points that help you
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avoiding reimplement existing behavior, and describes the difference
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between <code>"tbl"</code> and <code>"tbl_df"</code>.</p>
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<p>Read more in <a href="https://adv-r.hadley.nz/index.html">the second
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edition of Advanced R</a>:</p>
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<ul>
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<li>about the internal representation of data frames and tibbles in the
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<a href="https://adv-r.hadley.nz/vectors-chap.html#lists">Lists</a> and
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<a href="https://adv-r.hadley.nz/vectors-chap.html#tibble">Data frames
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and tibbles</a> sections of the <a href="https://adv-r.hadley.nz/vectors-chap.html">Vectors
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chapter</a>,</li>
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<li>about R’s S3 object-oriented system in the <a href="https://adv-r.hadley.nz/s3.html">S3 chapter</a>.</li>
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</ul>
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<div id="topics-documented-elsewhere" class="section level2">
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<h2>Topics documented elsewhere</h2>
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<ul>
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<li><p>Change or tweak the way a tibble prints:
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<code>vignette("extending", package = "pillar")</code></p></li>
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<li><p>Change or tweak the way a column type is printed in a tibble:
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<code>vignette("pillar", package = "vctrs")</code></p></li>
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<li><p>Implement a new column data type:
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<code>vignette("s3-vector", package = "vctrs")</code></p></li>
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<li><p>Making your tibble subclass work well with dplyr:
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<code>?dplyr::dplyr_extending</code></p></li>
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</ul>
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</div>
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<div id="data-frame-subclasses" class="section level2">
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<h2>Data frame subclasses</h2>
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<div class="sourceCode" id="cb1"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="fu">library</span>(tibble)</span></code></pre></div>
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<p>For tibble >= 3.0.0, the <code>"tbl"</code> class is responsible
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for printing, while the <code>"tbl_df"</code> class adds tibble’s sturdy
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subsetting and subset assignment behavior (see
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<code>vignette("invariants")</code> for details). This means that a data
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frame class that would like to (mostly) print like a tibble but keep the
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behavior from base R’s data frames can inherit from
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<code>c("tbl", "data.frame")</code> or just from <code>"tbl"</code>. An
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example is the <code>"tbl_sql"</code> class in the dbplyr package that
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is used to implement lazy database tables.</p>
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<div id="tibble-example" class="section level3">
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<h3>Tibble example</h3>
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<div class="sourceCode" id="cb2"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a>my_tbl_df <span class="ot"><-</span> <span class="fu">new_tibble</span>(</span>
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<span id="cb2-2"><a href="#cb2-2" aria-hidden="true" tabindex="-1"></a> <span class="fu">list</span>(<span class="at">a =</span> <span class="dv">1</span><span class="sc">:</span><span class="dv">3</span>, <span class="at">b =</span> <span class="dv">2</span><span class="sc">:</span><span class="dv">4</span>),</span>
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<span id="cb2-3"><a href="#cb2-3" aria-hidden="true" tabindex="-1"></a> <span class="at">class =</span> <span class="st">"my_tbl_df"</span></span>
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<span id="cb2-4"><a href="#cb2-4" aria-hidden="true" tabindex="-1"></a>)</span>
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<span id="cb2-5"><a href="#cb2-5" aria-hidden="true" tabindex="-1"></a></span>
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<span id="cb2-6"><a href="#cb2-6" aria-hidden="true" tabindex="-1"></a>tbl_sum.my_tbl_df <span class="ot"><-</span> <span class="cf">function</span>(x, ...) {</span>
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<span id="cb2-7"><a href="#cb2-7" aria-hidden="true" tabindex="-1"></a> <span class="fu">c</span>(</span>
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<span id="cb2-8"><a href="#cb2-8" aria-hidden="true" tabindex="-1"></a> <span class="st">"My custom tibble"</span> <span class="ot">=</span> <span class="st">"Some info about it"</span>,</span>
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||
<span id="cb2-9"><a href="#cb2-9" aria-hidden="true" tabindex="-1"></a> <span class="fu">NextMethod</span>()</span>
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<span id="cb2-10"><a href="#cb2-10" aria-hidden="true" tabindex="-1"></a> )</span>
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<span id="cb2-11"><a href="#cb2-11" aria-hidden="true" tabindex="-1"></a>}</span>
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<span id="cb2-12"><a href="#cb2-12" aria-hidden="true" tabindex="-1"></a></span>
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<span id="cb2-13"><a href="#cb2-13" aria-hidden="true" tabindex="-1"></a>my_tbl_df</span></code></pre></div>
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<pre><code>## # My custom tibble: Some info about it
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## # A tibble: 3 × 2
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## a b
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## <int> <int>
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## 1 1 2
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## 2 2 3
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## 3 3 4</code></pre>
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<div class="sourceCode" id="cb4"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true" tabindex="-1"></a>my_tbl_df[, <span class="st">"a"</span>]</span></code></pre></div>
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<pre><code>## # My custom tibble: Some info about it
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## # A tibble: 3 × 1
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## a
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## <int>
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## 1 1
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## 2 2
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## 3 3</code></pre>
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</div>
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<div id="data-frame-example" class="section level3">
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<h3>Data frame example</h3>
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<div class="sourceCode" id="cb6"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb6-1"><a href="#cb6-1" aria-hidden="true" tabindex="-1"></a>my_tbl <span class="ot"><-</span> vctrs<span class="sc">::</span><span class="fu">new_data_frame</span>(</span>
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<span id="cb6-2"><a href="#cb6-2" aria-hidden="true" tabindex="-1"></a> <span class="fu">list</span>(<span class="at">a =</span> <span class="dv">1</span><span class="sc">:</span><span class="dv">3</span>, <span class="at">b =</span> <span class="dv">2</span><span class="sc">:</span><span class="dv">4</span>),</span>
|
||
<span id="cb6-3"><a href="#cb6-3" aria-hidden="true" tabindex="-1"></a> <span class="at">class =</span> <span class="fu">c</span>(<span class="st">"my_tbl"</span>, <span class="st">"tbl"</span>)</span>
|
||
<span id="cb6-4"><a href="#cb6-4" aria-hidden="true" tabindex="-1"></a>)</span>
|
||
<span id="cb6-5"><a href="#cb6-5" aria-hidden="true" tabindex="-1"></a></span>
|
||
<span id="cb6-6"><a href="#cb6-6" aria-hidden="true" tabindex="-1"></a>tbl_sum.my_tbl <span class="ot"><-</span> <span class="cf">function</span>(x, ...) {</span>
|
||
<span id="cb6-7"><a href="#cb6-7" aria-hidden="true" tabindex="-1"></a> <span class="fu">c</span>(</span>
|
||
<span id="cb6-8"><a href="#cb6-8" aria-hidden="true" tabindex="-1"></a> <span class="st">"My custom data frame"</span> <span class="ot">=</span> <span class="st">"Some info about it"</span>,</span>
|
||
<span id="cb6-9"><a href="#cb6-9" aria-hidden="true" tabindex="-1"></a> <span class="fu">NextMethod</span>()</span>
|
||
<span id="cb6-10"><a href="#cb6-10" aria-hidden="true" tabindex="-1"></a> )</span>
|
||
<span id="cb6-11"><a href="#cb6-11" aria-hidden="true" tabindex="-1"></a>}</span>
|
||
<span id="cb6-12"><a href="#cb6-12" aria-hidden="true" tabindex="-1"></a></span>
|
||
<span id="cb6-13"><a href="#cb6-13" aria-hidden="true" tabindex="-1"></a>my_tbl</span></code></pre></div>
|
||
<pre><code>## # My custom data frame: Some info about it
|
||
## # A data frame: 3 × 2
|
||
## a b
|
||
## <int> <int>
|
||
## 1 1 2
|
||
## 2 2 3
|
||
## 3 3 4</code></pre>
|
||
<div class="sourceCode" id="cb8"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb8-1"><a href="#cb8-1" aria-hidden="true" tabindex="-1"></a>my_tbl[, <span class="st">"a"</span>]</span></code></pre></div>
|
||
<pre><code>## [1] 1 2 3</code></pre>
|
||
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|
||
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