Snippets of code for things you do all the time in R | Hacker News Reader

Snippets of code for things you do all the time in R

4dpiecharts.com

28 pointsjohn_horton13 comments

shameless plug: My book R Graph Cookbook is out soon - https://www.packtpub.com/r-graph-cookbook/book. It contains recipes for doing things with graphs, which can sometimes be obscure, annoying and time consuming.

Interesting - do you have a sample chapter you can make public?

(if there already is on the site you linked to, sorry for being obtuse).

Sample chapter coming up shortly. If you don't see it on the linked page in a couple of days, please email me (in profile).

This would be nice an format with short functions that could be upvoted (like hacker news comments). Three shortcuts is a rather limited start.

Clearly more a comment for an R forum, but why the hell does anybody bother using '<-' instead of '='? Are you trying to obfuscate?

Using '<-' is the general style of the R community. The accepted (but not universal) practice is to use '<-' for assignment and '=' in argument passing. This is a good idea because '<-' and '=' are not equivalent and '<-' is more likely the operator you want. From the help page [1] The operator ‘<-’ can be used anywhere, whereas the operator ‘=’ is only allowed at the top level (e.g., in the complete expression typed at the command prompt) or as one of the subexpressions in a braced list of expressions. That being said, some R community members still use '=' for assignment, but it's frowned upon. It certainly annoys me when I see it in R code.

Simple example to show when '=' won't work but '<-' will. Pilfered from "R Inferno" [2], which is an excellent reference for R idioms and best practices.

  system.time(vec1 <- rnorm(1000))
  mean(vec1)
  system.time(vec2 = rnorm(1000))
  mean(vec2)

And to demonstrate that you need to use '=' for argument passing:

  x <- c(3,4,NA)
  mean(x)
  mean(x, na.rm=TRUE)
  mean(x, na.rm<-TRUE)

[1] Type help('=') at an R prompt, or view it online: http://stat.ethz.ch/R-manual/R-patched/library/base/html/ass...

[2] http://www.burns-stat.com/pages/Tutor/R_inferno.pdf

edit: clarified statement.

edit: added examples.

I am of the opposite opinion, but perhaps I can be converted.

Do you have an example of where it would be required to use '<-'? Not just median(x <- 10), but a use in which there no simple '=' alternative.

I've added some examples to my above comment. My example is perhaps a little closer to 'median(x <- 10)' than you were asking for, but I think it illustrates the point that using '=' will not always have the desired result in places where '<-' would.

My problem is that between work in work and work in startup I need to write in about 8 languages.

This applies in all languages:

vec1 = rnorm(100)

system.time(vec1)

mean(vec1)

And, I can get my colleagues to fix it when I screw up, even though they are not R-heads.

You gotta do what you gotta do, but your example probably doesn't do what you want in R.

  > system.time(vec1 <- rnorm(1000000))
     user  system elapsed 
    0.200   0.000   0.199

My computer takes .2 seconds to generate the million random normals and assign them to vec1.

  > vec1 = rnorm(1000000)
  > system.time(vec1)
     user  system elapsed 
        0       0       0

My computer only takes 0 seconds to evaluate the existing vec1 of length one million.

Ah - sorry - I was being a bit t'ick, and didn't twig the time thing. Should I require it, I will keep it in mind. Thank you.

My understanding has always been that <- is the way that S did it, so that's the way R originally did it but = is almost always equivalent. I haven't found a place in my modest R hacking yet that = hasn't worked the way I expected it to...

And I haven't found anything in my ten years of using R in statistical analysis where '=' didn't work either. I've written a lot of R code. A hedge process on €2bn is being monitored with '=' signs as we speak. Dastardly.

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