is.R                  package:base                  R Documentation

Are we using R, rather than S?

Description:

     Test if running under R.

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, either your the code must 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.

See Also:

     `R.version', `system'.

Examples:

     x <- runif(20); small <- x < 0.4
     # `which()' only exists in R:
     if(is.R()) which(small) else seq(along=small)[small]

