knitr: A General-Purpose Package for Dynamic Report Generation in R

1 Installation
2 Motivation
3 Usage
4 License
Appendix

Title	A General-Purpose Package for Dynamic Report Generation in R
Version	1.49.7
Description	Provides a general-purpose tool for dynamic report generation in R using Literate Programming techniques.
Depends	R (>= 3.6.0)
Imports	evaluate (>= 0.15), highr (>= 0.11), methods, tools, xfun (>= 0.50), yaml (>= 2.1.19)
Suggests	bslib, codetools, DBI (>= 0.4-1), digest, formatR, gifski, gridSVG, htmlwidgets (>= 0.7), jpeg, JuliaCall (>= 0.11.1), magick, litedown, markdown (>= 1.3), png, ragg, reticulate (>= 1.4), rgl (>= 0.95.1201), rlang, rmarkdown, sass, showtext, styler (>= 1.2.0), targets (>= 0.6.0), testit, tibble, tikzDevice (>= 0.10), tinytex (>= 0.46), webshot, rstudioapi, svglite
License	GPL
URL	https://yihui.org/knitr/
BugReports	https://github.com/yihui/knitr/issues
VignetteBuilder	litedown, knitr
Author	Yihui Xie [aut, cre], Abhraneel Sarma [ctb], Adam Vogt [ctb], Alastair Andrew [ctb], Alex Zvoleff [ctb], Amar Al-Zubaidi [ctb], Andre Simon [ctb], Aron Atkins [ctb], Aaron Wolen [ctb], Ashley Manton [ctb], Atsushi Yasumoto [ctb], Ben Baumer [ctb], Brian Diggs [ctb], Brian Zhang [ctb], Bulat Yapparov [ctb], Cassio Pereira [ctb], Christophe Dervieux [ctb], David Hall [ctb], David Hugh-Jones [ctb], David Robinson [ctb], Doug Hemken [ctb], Duncan Murdoch [ctb], Elio Campitelli [ctb], Ellis Hughes [ctb], Emily Riederer [ctb], Fabian Hirschmann [ctb], Fitch Simeon [ctb], Forest Fang [ctb], Frank E Harrell Jr [ctb], Garrick Aden-Buie [ctb], Gregoire Detrez [ctb], Hadley Wickham [ctb], Hao Zhu [ctb], Heewon Jeon [ctb], Henrik Bengtsson [ctb], Hiroaki Yutani [ctb], Ian Lyttle [ctb], Hodges Daniel [ctb], Jacob Bien [ctb], Jake Burkhead [ctb], James Manton [ctb], Jared Lander [ctb], Jason Punyon [ctb], Javier Luraschi [ctb], Jeff Arnold [ctb], Jenny Bryan [ctb], Jeremy Ashkenas [ctb, cph], Jeremy Stephens [ctb], Jim Hester [ctb], Joe Cheng [ctb], Johannes Ranke [ctb], John Honaker [ctb], John Muschelli [ctb], Jonathan Keane [ctb], JJ Allaire [ctb], Johan Toloe [ctb], Jonathan Sidi [ctb], Joseph Larmarange [ctb], Julien Barnier [ctb], Kaiyin Zhong [ctb], Kamil Slowikowski [ctb], Karl Forner [ctb], Kevin Smith K. Smith [ctb], Kirill Mueller [ctb], Kohske Takahashi [ctb], Lorenz Walthert [ctb], Lucas Gallindo [ctb], Marius Hofert [ctb], Martin Modrák [ctb], Michael Chirico [ctb], Michael Friendly [ctb], Michal Bojanowski [ctb], Michel Kuhlmann [ctb], Miller Patrick [ctb], Nacho Caballero [ctb], Nick Salkowski [ctb], Niels Richard Hansen [ctb], Noam Ross [ctb], Obada Mahdi [ctb], Pavel N. Krivitsky [ctb], Pedro Faria [ctb], Qiang Li [ctb], Ramnath Vaidyanathan [ctb], Richard Cotton [ctb], Robert Krzyzanowski [ctb], Rodrigo Copetti [ctb], Romain Francois [ctb], Ruaridh Williamson [ctb], Sagiru Mati [ctb], Scott Kostyshak [ctb], Sebastian Meyer [ctb], Sietse Brouwer [ctb], Simon Bernard de Bernard [ctb], Sylvain Rousseau [ctb], Taiyun Wei [ctb], Thibaut Assus [ctb], Thibaut Lamadon [ctb], Thomas Leeper [ctb], Tim Mastny [ctb], Tom Torsney-Weir [ctb], Trevor Davis [ctb], Viktoras Veitas [ctb], Weicheng Zhu [ctb], Wush Wu [ctb], Zachary Foster [ctb], Zhian N. Kamvar [ctb], Posit Software, PBC [cph, fnd]

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).

1 Installation

You can install the stable version on CRAN:

install.packages('knitr')

You can also install the development version (hourly build) from https://yihui.r-universe.dev:

options(repos = c(
  yihui = 'https://yihui.r-universe.dev',
  CRAN = 'https://cloud.r-project.org'
))

install.packages('knitr')

2 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).

3 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.

4 License

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

Appendix

To cite the package knitr in publications, please use:

Xie Y (2025). knitr: A General-Purpose Package for Dynamic Report Generation in R. R package version 1.49.7, https://yihui.org/knitr/.

@Manual{,
  title = {knitr: A General-Purpose Package for Dynamic Report Generation in R},
  author = {Yihui Xie},
  year = {2025},
  note = {R package version 1.49.7},
  url = {https://yihui.org/knitr/},
}

Xie Y (2015). Dynamic Documents with R and knitr, 2nd edition. Chapman and Hall/CRC, Boca Raton, Florida. ISBN 978-1498716963, https://yihui.org/knitr/.

@Book{,
  title = {Dynamic Documents with {R} and knitr},
  author = {Yihui Xie},
  publisher = {Chapman and Hall/CRC},
  address = {Boca Raton, Florida},
  year = {2015},
  edition = {2nd},
  note = {ISBN 978-1498716963},
  url = {https://yihui.org/knitr/},
}

Xie Y (2014). “knitr: A Comprehensive Tool for Reproducible Research in R.” In Stodden V, Leisch F, Peng RD (eds.), Implementing Reproducible Computational Research. Chapman and Hall/CRC. ISBN 978-1466561595.

@InCollection{,
  booktitle = {Implementing Reproducible Computational Research},
  editor = {Victoria Stodden and Friedrich Leisch and Roger D. Peng},
  title = {knitr: A Comprehensive Tool for Reproducible Research in {R}},
  author = {Yihui Xie},
  publisher = {Chapman and Hall/CRC},
  year = {2014},
  note = {ISBN 978-1466561595},
}