R: Are we using R, rather than S?

is.R {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]

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