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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
by ltjohnson 16y ago
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/assignOps.html http://stat.ethz.ch/R-manual/R-patched/library/base/html/ass...
[2] http://www.burns-stat.com/pages/Tutor/R_inferno.pdf http://www.burns-stat.com/pages/Tutor/R_inferno.pdf
edit: clarified statement.
edit: added examples.
- hessenwolf 16y agoI 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.
- ltjohnson 16y agoI'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.
- hessenwolf 16y agoMy 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.
- ltjohnson 16y agoYou 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.
- hessenwolf 16y agoAh - 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.