knitr (version 0.7)

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)).

Usage

knit(input, output = NULL, tangle = FALSE, text = NULL, envir = parent.frame())
purl(...)

Arguments

input

path of the input file

output

path of the output file; if NULL, this function will try to guess and it will be under the current working directory

tangle

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

text

a character vector as an alternative way to provide the input file

envir

the environment in which the code chunks are to be evaluated (can use new.env() to guarantee an empty new environment)

...

arguments passed to knit

Value

• The compiled document is written into the output file, and the path of the output file is returned, but if the output path is NULL, the output is returned as a character vector.

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 a 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, the file extension is reserved; 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-out.ext. 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 the content of the input document is matched against all pattern lists to automatically which pattern list is being used. If automatic detection failed, the pattern list will be decided based on the filename extension of the input document. Rnw files use the list apat$rnw, tex uses the list apat$tex, brew uses apat$brew and HTML-like files use apat$html (e.g. html and md files). You can 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).

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: http://yihui.name/knitr/

The knitr main manual: https://github.com/downloads/yihui/knitr/knitr-manual.pdf

The knitr graphics manual: https://github.com/downloads/yihui/knitr/knitr-graphics.pdf

Examples

library(knitr)
(f = tempfile(fileext = ".Rnw"))
file.copy(system.file("examples", "knitr-minimal.Rnw", package = "knitr"), f, overwrite = TRUE)
knit(f)
## or setwd(dirname(f)); knit(basename(f))

purl(f)  # extract R code only

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