base (version 3.3.2)

name: Names and Symbols

Description

A ‘name’ (also known as a ‘symbol’) is a way to refer to R objects by name (rather than the value of the object, if any, bound to that name). as.name and as.symbol are identical: they attempt to coerce the argument to a name. is.symbol and the identical is.name return TRUE or FALSE depending on whether the argument is a name or not.

Usage

as.symbol(x)
is.symbol(x)
as.name(x)
is.name(x)

Arguments

x

object to be coerced or tested.

Value

For as.name and as.symbol, an R object of type "symbol" (see typeof). For is.name and is.symbol, a length-one logical vector with value TRUE or FALSE.

Details

Names are limited to 10,000 bytes (and were to 256 bytes in versions of R before 2.13.0). as.name first coerces its argument internally to a character vector (so methods for as.character are not used). It then takes the first element and provided it is not "", returns a symbol of that name (and if the element is NA_character_, the name is `NA`). as.name is implemented as as.vector(x, "symbol"), and hence will dispatch methods for the generic function as.vector. is.name and is.symbol are primitive functions.

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

See Also

call, is.language. For the internal object mode, typeof. plotmath for another use of ‘symbol’.

Examples

an <- as.name("arrg")
is.name(an) # TRUE
mode(an)   # name
typeof(an) # symbol