This function takes an input file, extracts the R code in it according to a
list of patterns, evaluates the code and writes the output in another file.
It can also tangle R source code from the input document (
purl() is a
knit(..., tangle = TRUE)). The
option can be used to also tangle the code of inline expressions (disabled by
knit( input, output = NULL, tangle = FALSE, text = NULL, quiet = FALSE, envir = parent.frame(), encoding = "UTF-8" )
purl(..., documentation = 1L)
The compiled document is written into the output file, and the path
of the output file is returned. If the
text argument is not
NULL, the compiled output is returned as a character vector. In
other words, if you provide a file input, you get an output filename; if
you provide a character vector input, you get a character vector output.
Path to the input file.
Path to the output file for
function will try to guess a default, which will be under the current
Boolean; whether to tangle the R code from the input file (like
A character vector. This is an alternative way to provide the input file.
Boolean; suppress the progress bar and messages?
Encoding of the input file; always assumed to be UTF-8 (i.e., this argument is effectively ignored).
arguments passed to
An integer specifying the level of documentation to add to
the tangled script.
0 means to output pure code, discarding all text chunks);
1 (the default) means to add the chunk headers to the code;
2 means to
add all text chunks to code as roxygen comments.
For most of the time, it is not necessary to set any options outside the
input document; in other words, a single call like
knit('my_input.Rnw') is usually enough. This function will try to
determine many internal settings automatically. For the sake of
reproducibility, it is better practice to include the options inside the
input document (to be self-contained), instead of setting them before
knitting the document.
First the filename of the output document is determined in this way:
foo.tex, and other filename extensions like
.Rmarkdown) will generate
respectively. For other types of files, if the filename contains
_knit_, this part will be removed in the output file, e.g.,
foo_knit_.html creates the output
foo.html; if _knit_ is
not found in the filename,
foo.ext will produce
ext is not
txt, otherwise the output is
tangle = TRUE,
foo.ext generates an R script
We need a set of syntax to identify special markups for R code chunks and R
options, etc. The syntax is defined in a pattern list. All built-in pattern
lists can be found in
all_patterns (call it
knitr will try to decide the pattern list based on the filename
extension of the input document, e.g. Rnw files use the list
apat$rnw, tex uses the list
apat$tex, brew uses
apat$brew and HTML files use
apat$html; for unkown extensions,
the content of the input document is matched against all pattern lists to
automatically determine which pattern list is being used. You can also
manually set the pattern list using the
knit_patterns object or
pat_rnw series functions in advance and knitr will
respect the setting.
According to the output format (
opts_knit$get('out.format')), a set of
output hooks will be set to mark up results from R (see
render_latex). The output format can be LaTeX, Sweave and HTML,
etc. The output hooks decide how to mark up the results (you can customize
knit comes from its counterpart weave (as in Sweave),
and the name
purl (as tangle in Stangle) comes from a knitting
method `knit one, purl one'.
If the input document has child documents, they will also be compiled
See the package website and manuals in the references to know more about knitr, including the full documentation of chunk options and demos, etc.
citation('knitr') for the citation information.
library(knitr) (f = system.file("examples", "knitr-minimal.Rnw", package = "knitr")) knit(f) # compile to tex purl(f) # tangle R code purl(f, documentation = 0) # extract R code only purl(f, documentation = 2) # also include documentation unlink(c("knitr-minimal.tex", "knitr-minimal.R", "figure"), recursive = TRUE)
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