[R] Most elegant way to use formals() in building functions
Frank E Harrell Jr
f.harrell at vanderbilt.edu
Sat Jul 25 00:35:18 CEST 2009
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.
Thanks
Frank
--
Frank E Harrell Jr Professor and Chair School of Medicine
Department of Biostatistics Vanderbilt University
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