is.language {base} | R Documentation |
Is an Object a Language Object?
Description
is.language
returns TRUE
if x
is a
variable name
, a call
, or an
expression
.
Usage
is.language(x)
Arguments
x |
object to be tested. |
Note
A name
is also known as ‘symbol’, from its type
(typeof
), see is.symbol
.
If typeof(x) == "language"
, then is.language(x)
is always true, but the reverse does not hold as expressions or
names y
also fulfill is.language(y)
, see the examples.
This is a primitive function.
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
Examples
ll <- list(a = expression(x^2 - 2*x + 1), b = as.name("Jim"),
c = as.expression(exp(1)), d = call("sin", pi))
sapply(ll, typeof)
sapply(ll, mode)
stopifnot(sapply(ll, is.language))
[Package base version 4.4.1 Index]