Create or test for objects of mode "call" (or "(", see Details).
call(name, …)
is.call(x)
as.call(x)| Parameter | Description |
|---|---|
name |
a non-empty character string naming the function to be called. |
… |
arguments to be part of the call. |
x |
an arbitrary R object. |
# NOT RUN {
is.call(call) #-> FALSE: Functions are NOT calls
## set up a function call to round with argument 10.5
cl <- call("round", 10.5)
is.call(cl) # TRUE
cl
identical(quote(round(10.5)), # <- less functional, but the same
cl) # TRUE
## such a call can also be evaluated.
eval(cl) # [1] 10
class(cl) # "call"
typeof(cl)# "language"
is.call(cl) && is.language(cl) # always TRUE for "call"s
A <- 10.5
call("round", A) # round(10.5)
call("round", quote(A)) # round(A)
f <- "round"
call(f, quote(A)) # round(A)
## if we want to supply a function we need to use as.call or similar
f <- round
# }
# NOT RUN {
call(f, quote(A)) # error: first arg must be character
# }
# NOT RUN {
(g <- as.call(list(f, quote(A))))
eval(g)
## alternatively but less transparently
g <- list(f, quote(A))
mode(g) <- "call"
g
eval(g)
## see also the examples in the help for do.call
# }