Scratching that itch from ifelse

September 3, 2014
By

(This article was first published on ECONinfo » Rblogger, and kindly contributed to R-bloggers)

Okay, as I wrote yesterday, ifelse is rather slow, at least compared to working in C++. As my current project is using ifelse rather a lot, i decided to write a small utility function. In the expectation that I will collect a number of similar functions, I made a package out of it and posted it on github: https://github.com/ojessen/ojUtils

I get a speedup of about 30 times, independent of the target type.

Feedback and corrections greatly appreciated.

Thanks to the people at Travis for providing a free CI server which works directly with github. This of course is a tiny example, but it is good to know that the workflow to set this up can be done in 5 minutes.

And thanks to Romain Fraoncois for showing some Rcpp sugar:

Some data:

require(ojUtils)
## Loading required package: ojUtils
require(microbenchmark)
## Loading required package: microbenchmark
test = sample(c(T,F), size = 1e5, T)
yes = runif(1e5)
no = runif(1e5)

microbenchmark(ifelse(test, yes, no), ifelseC(test, yes, no))
## Loading required package: Rcpp
## Unit: microseconds
##                    expr   min      lq  median      uq    max neval
##   ifelse(test, yes, no) 31925 33404.8 34065.1 58083.5  71891   100
##  ifelseC(test, yes, no)   620   647.5   721.8   817.7 209254   100
test = sample(c(T,F), size = 1e5, T)
yes = rep("a", 1e5)
no = rep("b", 1e5)

microbenchmark(ifelse(test, yes, no), ifelseC(test, yes, no))
## Unit: milliseconds
##                    expr    min     lq median     uq   max neval
##   ifelse(test, yes, no) 57.313 58.763 59.626 72.435 87.92   100
##  ifelseC(test, yes, no)  1.747  1.837  1.926  2.749 29.56   100
test = sample(c(T,F), size = 1e5, T)
yes = rep(1L, 1e5)
no = rep(2L, 1e5)

microbenchmark(ifelse(test, yes, no), ifelseC(test, yes, no))
## Unit: microseconds
##                    expr     min      lq  median      uq   max neval
##   ifelse(test, yes, no) 30747.6 31868.5 32274.8 32829.0 59412   100
##  ifelseC(test, yes, no)   453.7   548.9   581.5   646.2 27575   100
test = sample(c(T,F), size = 1e5, T)
yes = rep(T, 1e5)
no = rep(F, 1e5)

microbenchmark(ifelse(test, yes, no), ifelseC(test, yes, no))
## Unit: microseconds
##                    expr     min      lq  median      uq   max neval
##   ifelse(test, yes, no) 29331.2 31167.3 31719.7 32455.3 60589   100
##  ifelseC(test, yes, no)   460.1   537.1   566.8   640.7 27118   100

To leave a comment for the author, please follow the link and comment on his blog: ECONinfo » Rblogger.

R-bloggers.com offers daily e-mail updates about R news and tutorials on topics such as: visualization (ggplot2, Boxplots, maps, animation), programming (RStudio, Sweave, LaTeX, SQL, Eclipse, git, hadoop, Web Scraping) statistics (regression, PCA, time series, trading) and more...



If you got this far, why not subscribe for updates from the site? Choose your flavor: e-mail, twitter, RSS, or facebook...

Comments are closed.