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Lessons Learned in Developing R Packages

Yihui Xie

Department of Statistics, Iowa State University
Computational Statistics working group

Nov 2, 2011 (i.e. 20111102)


Nothing here; move on!

Do we have to suffer from software?

How difficult is it to use the Linux servers in our department?

Why not RStudio?

say goodbye to the command nohup since we can use the web interface

On Design


What Should I Say...

Q: How to Make Developers Happier?

A: You do not have to buy me beer, but please just do not let me see you use an R version released 2 years ago

animation: Start with Naive Ideas

the best time to write a package was 5 years ago, and...

  ## rotate the word 'Animation'
  for (i in 1:360) {
    plot(1, ann = FALSE, type = "n", axes = FALSE)
    text(1, 1, "Animation", 
      srt = i, col = rainbow(360)[i], cex = 7 * i/360)

animation: Demos and Examples

do not expect beginners to read source code, and do not expect experts to read documentation, either!

  demo('fire')  # an application of image()

animation: Demos and Examples (cont'd)

examples are fast guides to usage

  ## this gives you an overview of the package
  • images are supported in documentation in R 2.14 (use \figure{})
  • should be possible to create figures dynamically with Sweave in future
  • honestly, I do not like the old style of R documentation at all

animation: Interfaces

  • why ani.start() and ani.stop() became saveHTML()
  • use modern CSS elements (round corners and shadow, etc) rather than the old clunky styles
  • make it appealing enough that the user cannot wait clicking the button!

animation: Automatic Configurations


animation: Automatic Configurations (cont'd)

  • saveGIF() uses ImageMagick or GraphicsMagick to convert images to GIF animations; need to know where they are installed
  • automatically search for ImageMagick in Windows Registry Hive using readRegistry() (very likely to succeed)
  • instead of teaching what is the environmental variable PATH (very frustrating thanks to “the system that is just this tall”)

animation: What Do I Regret Today?

  • function names: now I'm more in favor of foo_bar than foo.bar (why? S3 generic functions) or fooBar (why? _ is a clearer separator than capital letters)
  • built a Wiki site too early and it is too big to maintain (http://animation.yihui.name); I should have used tools like Sweave to build it dynamically (my new package knitr was partly motivated from here)

formatR: Computing on the Code

  • R can compute on its own code: parse() and deparse()
  • the formatR package uses the side effect of them to reformat R code
  • you give me 1+1 and I return you 1 + 1 (what the heck is the difference?)

well, compare

for(k in 1:10){j=cos(sin(k)*k^2)+3;print(j-5)}


for (k in 1:10) {
    j = cos(sin(k) * k^2) + 3
    print(j - 5)

formatR: Motivation

  • it is not the fault of people to create “long chunks of ill-formatted R code piled beside the Snedecor-Grad-Copier printer”
  • why cannot a workman blame his tools?
  • Stat579 students motivated the tidy.eval() function

I frown on this in homeworks (score: 99.5):

> 1+1
[1] 2

tidy.eval() does this (score: 100):

1 + 1
## [1] 2

Rd2roxygen: Escaping the Rd Inferno

Rd2roxygen: How I Regained Enthusiasm from roxygen

  • I was once extremely frustrated at maintaining the animation package due to documentation
  • idea of roxygen: source code and documentation are in the same file
##' This is title
##' @param a documentation for argument a
##' @param b documentation for argument b
f = function(a, b) {
  • no longer needs to switch back and forth between R/f.R and man/f.Rd
  • documentation is generated dynamically

Rd2roxygen: How to Escape the Inferno

  • roxygen translates comments to Rd
  • Rd2roxygen translates Rd back to roxygen comments, e.g.


  \item{a}{documentation for argument a}


##' @param a documentation for argument a
  • you maintain a single source from now on

GitHub: One Command to Fork em All

Why Version Control?

  • keep track of what you have been doing (accumulatively)
  • a proof of hard work to your advisor
  • save tears when your system crashes
  • much much easier collaboration with others
  • ...
  • why GitHub? community, easy collaboration, ... (compare to R-Forge)

Why do I use = instead of <-?

  • it is simpler to type (although Emacs/ESS binds <- to _)
  • almost all other languages use =
  • it does not confuse me at all (main reason why some people are against recommend =)

Names: Important!

  • can you remember the name CvM2SL2Test or HumMeth27QCReport
  • if people cannot even remember your name, how are you supposed to be famous/popular?
  • Hadley's principle: Google-able
  • an unbeatable name: lubridate

Have Fun

  • the fun package: games and fun
  • animation: started from fun
  • cranvas: interactive graphics is fun
  • knitr (an alternative to Sweave): dynamic report is fun
  • ...

Aim at Problems, Instead of Killing the Dragon