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:

.@ojessen I sent you a pull request leveraging Rcpp’s ifelse. Although maybe wait: Rcpp’s ifelse is broken … https://t.co/38P0mQc3aZ

— Romain Francois (@romain_francois) 20. Juni 2014

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