# is.R

0th

Percentile

##### Are we using R, rather than S?

Test if running under R.

Keywords
utilities, environment
##### Usage
is.R()
##### Details

The function has been written such as to correctly run in all versions of R, S and S-PLUS. In order for code to be runnable in both R and S dialects previous to S-PLUS 8.0, your code must either define is.R or use it as

if (exists("is.R") && is.function(is.R) && is.R()) {  ## R-specific code } else {  ## S-version of code }

##### Value

is.R returns TRUE if we are using R and FALSE otherwise.

R.version, system.
library(base) x <- stats::runif(20); small <- x < 0.4 ## In the early years of R, 'which()' only existed in R: if(is.R()) which(small) else seq(along = small)[small]