# knitr v1.22

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## A General-Purpose Package for Dynamic Report Generation in R

Provides a general-purpose tool for dynamic report generation in R using Literate Programming techniques.

# knitr

The R package knitr is a general-purpose literate programming engine, with lightweight API's designed to give users full control of the output without heavy coding work. It combines many features into one package with slight tweaks motivated from my everyday use of Sweave. See the package homepage for details and examples. See FAQ's for a list of frequently asked questions (including where to ask questions).

## Installation

You can install the stable version on CRAN:

install.packages('knitr')


You can also install the development version from XRAN, which provides daily build of knitr:

# update all existing packages first
update.packages(ask = FALSE, repos = 'https://cran.r-project.org')
install.packages('knitr', repos = c('https://xran.yihui.name', 'https://cran.r-project.org'))


Note that if you want to build the source package via R CMD INSTALL without a previously installed version of knitr, you must either pre-install knitr from CRAN, or run R CMD INSTALL on this source repo, otherwise R CMD build will fail (which is probably a bug of base R).

## Motivation

While Sweave and related add-on packages like cacheSweave and pgfSweave are fairly good engines for literate programming in R, I often feel my hands are tied. For example:

• I stared at the source code of Sweave and wished for hundreds of times, if only I could easily insert [width=.8\textwidth] between \includegraphics and {my-plot.pdf}. (The official way in Sweave is \setkeys{Gin} but it is setting a global width, which is unrealistic since we often have to set widths individually; yes, you can use \setkeys{Gin} for many times, but why not just provide an option for each chunk?)
• I wished for many times, if only I could use graphics devices other than PDF and postscript; now the dream has come true in the official R, but what I was hoping for was an option as simple as dev = 'png' or dev = 'CairoJPEG'.
• I wished multiple plots in a code chunk could be recorded instead of only the last one.
• I wished there was a way to round the numbers in \Sexpr{} other than writing expressions like \Sexpr{round(x, 3)} for each single \Sexpr{}
• I wished I did not have to print() plots from. ggplot2 and a simple qplot(x, y) would just give me a plot in Sweave.
• I wished users would never need instructions on Sweave.sty or run into troubles due to the fact that LaTeX cannot find Sweave.sty.
• I wished cacheSweave could print the results of a code chunk even if it was cached.
• I wished brew could support graphics.
• I wished R2HTML could support R code syntax highlighting.
• ...

The package knitr was designed to give the user access to every part of the process of dealing with a literate programming document, so there is no need to hack at any core components if you want more freedom. I have gone through the source code of pgfSweave and cacheSweave for a couple of times and I often feel uncomfortable with the large amount of code copied from official R, especially when R has a new version released (I will begin to worry if the add-on packages are still up-to-date with the official Sweave).

## Usage

library(knitr)
?knit
knit(input)


If options are not explicitly specified, knitr will try to guess reasonable default settings. A few manuals are available such as the main manual, and the graphics manual. For a more organized reference, see the knitr book.

This package is free and open source software, licensed under GPL.

## Functions in knitr

 Name Description hook_movecode Some potentially useful document hooks hook_ffmpeg_html Hooks to create animations in HTML output knit_exit Exit knitting early knit2pdf Convert Rnw or Rrst files to PDF raw_block Mark character strings as raw blocks in R Markdown knit_expand A simple macro preprocessor for templating purposes rand_seed An unevaluated expression to return .Random.seed if exists knit2wp Knit an R Markdown document and post it to WordPress stitch Automatically create a report based on an R script and a template hook_pdfcrop Built-in chunk hooks to extend knitr fig_chunk Obtain the figure filenames for a chunk vignette_engines Package vignette engines include_url Embed a URL as an HTML iframe or a screenshot in knitr documents inline_expr Wrap code using the inline R expression syntax fig_path Path for figure files knit_params Extract knit parameters from a document knit_params_yaml Extract knit parameters from YAML text dep_prev Make later chunks depend on previous chunks engine_output An output wrapper for language engine output imgur_upload Upload an image to imgur.com knit_child Knit a child document hook_plot_html Default plot hooks for different output formats knit_engines Engines of other languages knit_rd Knit package documentation knit_patterns Patterns to match and extract R code in a document kable Create tables in LaTeX, HTML, Markdown and reStructuredText image_uri Encode an image file to a data URI knit_print A custom printing function knit_hooks Hooks for R code chunks, inline R code and output knit_theme Syntax highlighting themes knit_watch Watch an input file continuously and knit it when it is updated read_rforge Read source code from R-Forge include_graphics Embed external images in knitr documents knit_meta Metadata about objects to be printed opts_hooks Hooks for code chunk options knitr-package A general-purpose tool for dynamic report generation in R opts_knit Options for the knitr package knit2html Convert markdown to HTML using knit() and markdownToHTML() knit2pandoc Convert various input files to various output files using knit() and Pandoc extract_raw_output Mark character strings as raw output that should not be converted knit Knit a document set_header Set the header information read_chunk Read chunks from an external script opts_template Template for creating reusable chunk options wrap_rmd Wrap long lines in Rmd files knit_filter Spell check filter for source documents render_html Set output hooks for different output formats set_parent Specify the parent document of child documents knit_global The global environment in which code chunks are evaluated load_cache Load the cache database of a code chunk write_bib Generate BibTeX bibliography databases for R packages pat_rnw Set regular expressions to read input documents rocco Knit R Markdown using the classic Docco style opts_chunk Default and current chunk options is_latex_output Check if the current output type is LaTeX or HTML pandoc A Pandoc wrapper to convert documents to other formats rst2pdf A wrapper for rst2pdf set_alias Set aliases for chunk options spin Spin goat's hair into wool plot_crop Crop a plot (remove the edges) using PDFCrop or ImageMagick spin_child Spin a child R script all_patterns All built-in patterns asis_output Mark an R object with a special class clean_cache Clean cache files that are probably no longer needed combine_words Combine multiple words into a single string current_input Query the current input filename dep_auto Build automatic dependencies among chunks Sweave2knitr Convert Sweave to knitr documents all_labels Get all chunk labels in a document cache_engines Cache engines of other languages No Results!

## Vignettes of knitr

 Name assets/template-refcard.tex datatables.Rmd docco-classic.Rmd docco-linear.Rmd knit_expand.Rmd knit_print.Rmd knitr-html.Rhtml knitr-intro.Rmd knitr-markdown.Rmd knitr-refcard.Rmd knitr-refcard.lyx No Results!