R help - Dec 2013 - Simple way to define a function to be used in a formula object inside another function

I would like to do this:

f <- function(formula, data=NULL) {
  gg <- sqrt
  model.frame(formula, data=data)
  }
x <- y <- 1:10
f(y ~ gg(x))
Error in eval(expr, envir, enclos) : could not find function "gg"

Is there a simple way to get access to gg from within the model.frame 
invocation inside f?

Thanks
Frank

The following works because model.frame looks for things in environment(formula)
and ancestral environments thereof.  It puts the new things in a child
environment
of the original environment(formula) so it does not alter the original
environment.

f2 <- function (formula, data = NULL) 
{
    environment(formula) <- new.env(parent = environment(formula))
    assign(envir = environment(formula), "gg", sqrt)
    model.frame(formula, data = data)
}

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at
r-project.org] On Behalf
> Of Frank Harrell
> Sent: Sunday, December 15, 2013 10:09 AM
> To: RHELP
> Subject: [R] Simple way to define a function to be used in a formula object
inside another
> function
> 
> I would like to do this:
> 
> f <- function(formula, data=NULL) {
>   gg <- sqrt
>   model.frame(formula, data=data)
>   }
> x <- y <- 1:10
> f(y ~ gg(x))
> Error in eval(expr, envir, enclos) : could not find function "gg"
> 
> Is there a simple way to get access to gg from within the model.frame
> invocation inside f?
> 
> Thanks
> Frank
> 
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> and provide commented, minimal, self-contained, reproducible code.

Thank you Bill, that worked perfectly.
Frank