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 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.

### See Also

`R.version`

, `system`

.

### Examples

```
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]
```

[Package

*base* version 4.3.0

Index]