knit_expand.Rmd

Demos of knit_expand()

A few simple examples:

library(knitr) knit_expand(text = 'The value of pi is {{pi}}.') knit_expand(text = 'The value of a is {{a}}, so a + 1 is {{a+1}}.', a = rnorm(1)) knit_expand(text = 'The area of a circle with radius {{r}', r = 5)

Any number of variables:

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)

Custom delimiter <% %>:

knit_expand(text = 'I do not like curly braces, so use % with <> instead: a is <% a %>.', a = 8, delim = c("<%", "%>"))

The pyexpander delimiter:

knit_expand(text = 'hello $(LETTERS[24]) and $(pi)!', delim = c("$(", ")"))

Arbitrary R code:

knit_expand(text = 'you cannot see the value of x {{x=rnorm(1)}}but it is indeed created: x = {{x}}') res = knit_expand(text = c(' x | x^2', '{{x=1:5;paste(sprintf("%2d | %3d", x, x^2), collapse = "\n")}}')) cat(res)

The m4 example: http://en.wikipedia.org/wiki/M4_(computer_language)

res = knit_expand(text = c('{{i=0;h2=function(x){i<<-i+1;sprintf("

%d. %s

", i, x)} }}', '{{h2("First Section")}}', '{{h2("Second Section")}}', '{{h2("Conclusion")}}', '')) cat(res)

Build regression models based on a template; loop through all variables in mtcars:

src = lapply(names(mtcars)[-1], function(i) { knit_expand(text=c("# Regression on {{i}}", '```{r}, data=mtcars)', '```')) }) # knit the source res = knit_child(text = unlist(src)) res = paste('
', gsub('^\\s*|\\s*$', '', res), '
', sep = '')

r res