[R] environments

[Setzer.Woodrow@epamail.epa.gov]

I would like to be able, inside a function, to create a new function, and
use it as part of a formula as an argument to, say, gnls or nlme.  for
example:

MyTop <- function(data=dta) {
     Cexp <- function(dose,A,B,m){...}
     Model <- as.formula(paste("y","~ Cexp(",paste(formals(Cexp),collapse
=", "),")"))
     MyCall <- call("gnls",Model,dta,...)
     eval(MyCall)
}

where "..." indicates I've left out unimportant details.  In practice, the
function Cexp would be the result of some computations.

When I actually try this, I get an error return with the message "Cexp not
found".  Is there a way around this?  I know I can use "Cexp <<- ...", but
I'm trying to find a "clean" solution.  Thanks.

R. Woodrow Setzer, Jr.                                            Phone:
(919) 541-0128
Experimental Toxicology Division                       Fax:  (919) 541-5394
Pharmacokinetics Branch
NHEERL MD-74; US EPA; RTP, NC 27711

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