Duncan Murdoch wrote:
On 24/07/2009 6:35 PM, Frank E Harrell Jr wrote:
Dear Group:
I want to create a function having a ... argument and to have the
default arguments evaluated, as thus:
g <- function(a, b, ...) a+b
formals(g) <- alist(a=,b=2+3,...=)
g
function (a, b = 2 + 3, ...)
a + b
But I want the default argument for b to be evaluated as 5. How can
this be done? Note: My real need is for a more complex expression to
be evaluated for the default value of an argument.
I can use formals(g) <- list(a=NULL, b=2+3, ...=NULL) but then
list(...) doesn't behave properly in the function.
Not sure if it's "most elegant", but I think this works:
formals(g) <- eval(substitute(alist(a=,b=default,...=),
list(default=2+3)))
Duncan Murdoch
Thank you Duncan. That works perfectly.
Frank
--
Frank E Harrell Jr Professor and Chair School of Medicine
Department of Biostatistics Vanderbilt University
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