| 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