R: Names and Symbols

name {base} | R Documentation

## 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.

### 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.

### 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`.

### Note

The term ‘symbol’ is from the LISP background of R, whereas ‘name’ has been the standard S term for this.

### 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

[Package base version 2.15.1 Index]