knitr (version 1.20)

knit: Knit a document

Description

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 wrapper to knit(..., tangle = TRUE)). The knitr.purl.inline option can be used to also tangle the code of inline expressions (disabled by default).

Usage

knit(input, output = NULL, tangle = FALSE, text = NULL, quiet = FALSE, 
    envir = parent.frame(), encoding = getOption("encoding"))
purl(..., documentation = 1L)

Arguments

input

Path to the input file.

output

Path to the output file for knit(). If NULL, this function will try to guess a default, which will be under the current working directory.

tangle

Boolean; whether to tangle the R code from the input file (like Stangle).

text

A character vector. This is an alternative way to provide the input file.

quiet

Boolean; suppress the progress bar and messages?

envir

Environment in which code chunks are to be evaluated, for example, parent.frame(), new.env(), or globalenv()).

encoding

Encoding of the input file; see file.

...

arguments passed to knit() from purl()

documentation

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.

Value

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.

Details

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.Rnw generates foo.tex, and other filename extensions like .Rtex, .Rhtml (.Rhtm) and .Rmd (.Rmarkdown) will generate .tex, .html and .md 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 foo.txt if ext is not txt, otherwise the output is foo-out.txt. If tangle = TRUE, foo.ext generates an R script foo.R.

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 apat). First 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 the 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 the hooks).

The name 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 recursively. See knit_child.

See the package website and manuals in the references to know more about knitr, including the full documentation of chunk options and demos, etc.

References

Package homepage: https://yihui.name/knitr/. The knitr main manual: and graphics manual.

See citation('knitr') for the citation information.

Examples

# NOT RUN {
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
# }