list(...) as.list(x) is.list(x) alist(...)
list
are of the form value
or tag=value
.
The function returns a list composed of its arguments
with each value either tagged or untagged,
depending on how the argument was specified.
alist
is like list
, except in the handling of tagged
arguments with no value. These are handled as if they described
function arguments with no default (cf. formals
), whereas
list
simply ignores them.
as.list
attempts to coerce its argument to list type.
For functions, this returns the concatenation of the list of formals
arguments and the function body. For expressions, the list of
constituent calls is returned.
is.list
returns TRUE
if its argument
is a list and FALSE
otherwise.
To create an empty list, it is necessary to use the
function vector
with a mode
of "list"
.
vector(., mode="list")
, c
, for concatenation;
formals
.data(cars) # create a plotting structure pts <- list(x=cars[,1], y=cars[,2]) plot(pts) # Argument lists f <- function()x formals(f) <- alist(x=, y=2, ...=) # Note the spec. of a "..." argument f