2025-01-12 04:36:52 +08:00

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#LyX 2.0 created this file. For more info see http://www.lyx.org/
\lyxformat 413
\begin_document
\begin_header
\textclass article
\use_default_options true
\begin_modules
knitr
\end_modules
\maintain_unincluded_children false
\language english
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\secnumdepth 3
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\listings_params "language=R"
\tracking_changes false
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\html_math_output 0
\html_css_as_file 0
\html_be_strict false
\end_header
\begin_body
\begin_layout Standard
\begin_inset ERT
status open
\begin_layout Plain Layout
<<setup, include=FALSE, cache=FALSE>>=
\end_layout
\begin_layout Plain Layout
library(knitr)
\end_layout
\begin_layout Plain Layout
opts_chunk$set(fig.path = 'figure/listings-')
\end_layout
\begin_layout Plain Layout
options(formatR.arrow = TRUE)
\end_layout
\begin_layout Plain Layout
render_listings()
\end_layout
\begin_layout Plain Layout
@
\end_layout
\end_inset
\end_layout
\begin_layout Title
Using listings with knitr
\end_layout
\begin_layout Author
Yihui Xie
\end_layout
\begin_layout Standard
To use the
\series bold
listings
\series default
package with
\series bold
knitr
\series default
, all you need to do is to call a function in your first setup chunk (that
chunk should be hidden from the output with
\family typewriter
include=FALSE
\family default
and should not be cached):
\end_layout
\begin_layout Standard
\begin_inset ERT
status open
\begin_layout Plain Layout
% I just want to echo the 2nd line
\end_layout
\begin_layout Plain Layout
<<setup, echo=2>>=
\end_layout
\begin_layout Plain Layout
@
\end_layout
\end_inset
\end_layout
\begin_layout Standard
This function modifies the output hooks and header information so that the
output is written in
\series bold
listings
\series default
environments, which are kindly provided by Frank Harrell and can be found
in
\begin_inset Flex URL
status collapsed
\begin_layout Plain Layout
https://github.com/yihui/knitr/blob/master/inst/misc/Sweavel.sty
\end_layout
\end_inset
.
Of course you have to install the
\series bold
listings
\series default
package if your LaTeX toolset does not include this package.
\end_layout
\begin_layout Standard
Now we can see how the results look like with our new settings:
\end_layout
\begin_layout Standard
\begin_inset ERT
status open
\begin_layout Plain Layout
<<boring-random>>=
\end_layout
\begin_layout Plain Layout
set.seed(1121) # for reproducibility
\end_layout
\begin_layout Plain Layout
options(width=85)
\end_layout
\begin_layout Plain Layout
x=rnorm(20)
\end_layout
\begin_layout Plain Layout
x
\end_layout
\begin_layout Plain Layout
mean(x)
\end_layout
\begin_layout Plain Layout
sqrt(-1) # this will give you a warning message
\end_layout
\begin_layout Plain Layout
@
\end_layout
\end_inset
\end_layout
\begin_layout Standard
Another chunk:
\end_layout
\begin_layout Standard
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status open
\begin_layout Plain Layout
<<rgl-hook-demo,eval=FALSE>>=
\end_layout
\begin_layout Plain Layout
hook_rgl = function(before, options, envir) {
\end_layout
\begin_layout Plain Layout
## after a chunk has been evaluated
\end_layout
\begin_layout Plain Layout
if (before || !require('rgl') || rgl.cur() == 0) return() # no active
device
\end_layout
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name = paste(valid_prefix(options$fig.path), options$label, sep = '')
\end_layout
\begin_layout Plain Layout
par3d(windowRect = 100 + options$dpi * c(0, 0, options$width, options$height
))
\end_layout
\begin_layout Plain Layout
Sys.sleep(.05) # need time to respond to window size change
\end_layout
\begin_layout Plain Layout
\end_layout
\begin_layout Plain Layout
fmt = opts_knit$get('out.format')
\end_layout
\begin_layout Plain Layout
if (fmt %in% c('html', 'markdown', 'gfm', 'jekyll')) options$dev = 'png'
\end_layout
\begin_layout Plain Layout
\end_layout
\begin_layout Plain Layout
## support 3 formats: eps, pdf and png (default)
\end_layout
\begin_layout Plain Layout
switch(options$dev,
\end_layout
\begin_layout Plain Layout
postscript = rgl.postscript(paste(name, '.eps', sep = ''), fmt
= 'eps'),
\end_layout
\begin_layout Plain Layout
pdf = rgl.postscript(paste(name, '.pdf', sep = ''), fmt = 'pdf'),
\end_layout
\begin_layout Plain Layout
rgl.snapshot(paste(name, '.png', sep = ''), fmt = 'png'))
\end_layout
\begin_layout Plain Layout
\end_layout
\begin_layout Plain Layout
if (fmt == 'html') return(.plot.hook.html(c(name, 'png'), options))
\end_layout
\begin_layout Plain Layout
if (fmt %in% c('markdown', 'gfm', 'jekyll'))
\end_layout
\begin_layout Plain Layout
return(.plot.hook.markdown(c(name, 'png'), options))
\end_layout
\begin_layout Plain Layout
\end_layout
\begin_layout Plain Layout
paste(ifelse(options$align == 'center', '
\backslash
\backslash
centering{}', ''), '
\backslash
\backslash
includegraphics[',
\end_layout
\begin_layout Plain Layout
sprintf('width=%s', options$out.width), ']{', name, '}
\backslash
n', sep = '')
\end_layout
\begin_layout Plain Layout
}
\end_layout
\begin_layout Plain Layout
@
\end_layout
\end_inset
\end_layout
\begin_layout Standard
Well, we can do crazier things with
\series bold
knitr
\series default
.
Here we use the
\family typewriter
fig.cap
\family default
option to write plots into the
\family typewriter
figure
\family default
environment automatically, and the caption is generated from data dynamically
(see Figure
\begin_inset ERT
status collapsed
\begin_layout Plain Layout
\backslash
ref{fig:boxplot-ex}
\end_layout
\end_inset
):
\end_layout
\begin_layout Standard
\begin_inset ERT
status open
\begin_layout Plain Layout
% set an option first
\end_layout
\begin_layout Plain Layout
<<eval-opts, echo=FALSE>>=
\end_layout
\begin_layout Plain Layout
opts_knit$set(eval.after = 'fig.cap') # evaluate fig.cap after the chunk
\end_layout
\begin_layout Plain Layout
\end_layout
\begin_layout Plain Layout
<<boxplot-ex, fig.height=2, out.width='.8
\backslash
\backslash
linewidth', fig.cap=sprintf('This is a boxplot; the median is %.2f.', median(x))>>=
\end_layout
\begin_layout Plain Layout
par(mar=c(4,4,.1,.1))
\end_layout
\begin_layout Plain Layout
boxplot(x, horizontal=TRUE)
\end_layout
\begin_layout Plain Layout
@
\end_layout
\end_inset
\end_layout
\begin_layout Standard
As we know,
\family typewriter
figure
\family default
is a float environment, so it has floated away from the R code to the top
of this page.
This should not be surprising to LaTeX users.
\end_layout
\begin_layout Standard
You should be able to compile the TeX document and get a PDF file like this
one:
\begin_inset Flex URL
status collapsed
\begin_layout Plain Layout
https://github.com/yihui/knitr/releases/download/doc/knitr-listings.pdf
\end_layout
\end_inset
.
For more information about out hooks, see
\begin_inset Flex URL
status collapsed
\begin_layout Plain Layout
https://yihui.org/knitr/hooks/
\end_layout
\end_inset
.
\end_layout
\end_body
\end_document