68 lines
1.8 KiB
Plaintext
68 lines
1.8 KiB
Plaintext
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---
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title: Templating with knit_expand()
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author: Yihui Xie
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date: "`{r} Sys.Date()`"
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output:
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litedown::html_format:
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meta:
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css: ["@default"]
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---
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<!--
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%\VignetteEngine{litedown::vignette}
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%\VignetteIndexEntry{Templating with knit_expand()}
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-->
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A few simple examples:
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```{r}
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library(knitr)
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knit_expand(text = 'The value of pi is {{pi}}.')
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knit_expand(text = 'The value of a is {{a}}, so a + 1 is {{a+1}}.', a = rnorm(1))
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knit_expand(text = 'The area of a circle with radius {{r}} is {{pi*r^2}}', r = 5)
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```
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Any number of variables:
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```{r}
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knit_expand(text = 'a is {{a}} and b is {{b}}, with my own pi being {{pi}} instead of {{base::pi}}', a=1, b=2, pi=3)
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```
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Custom delimiter `<% %>`:
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```{r}
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knit_expand(text = 'I do not like curly braces, so use % with <> instead: a is <% a %>.', a = 8, delim = c("<%", "%>"))
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```
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The pyexpander delimiter:
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```{r}
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knit_expand(text = 'hello $(LETTERS[24]) and $(pi)!', delim = c("$(", ")"))
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```
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Arbitrary R code:
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```{r}
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knit_expand(text = 'you cannot see the value of x {{x=rnorm(1)}}but it is indeed created: x = {{x}}')
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res = knit_expand(text = c(' x | x^2', '{{x=1:5;paste(sprintf("%2d | %3d", x, x^2), collapse = "\n")}}'))
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cat(res)
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```
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The m4 example: <https://en.wikipedia.org/wiki/M4_(computer_language)>
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```{r}
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res = knit_expand(text = c('{{i=0;h2=function(x){i<<-i+1;sprintf("<h2>%d. %s</h2>", i, x)} }}<html>',
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'{{h2("First Section")}}', '{{h2("Second Section")}}', '{{h2("Conclusion")}}', '</html>'))
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cat(res)
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```
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Build regression models based on a template; loop through some variables in `mtcars`:
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```{r, comment=''}
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src = lapply(names(mtcars)[2:5], function(i) {
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knit_expand(text=c("# Regression on {{i}}", '```{r lm-{{i}}}', 'lm(mpg~{{i}}, data=mtcars)', '```', ''))
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})
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# knit the source
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litedown::fuse(unlist(src), 'markdown')
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```
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