model.frame() call from inside a function (PR#3671)

On 7 Aug 2003, Peter Dalgaard BSA wrote:

[[ I did discover yesterday (or maybe I was just reminded...) that we
even have nonstandard nonstandard evaluation rules in some places
(nls() seems to evaluate its model formula in the global environment
even if it is given explicitly within a function:

  f <- function() {
    g <- function(a,x) exp(-a*x)
    nls(y~g(a,x),start=list(a=.1))
  }
  x <- 1:10
  y <- exp(-.12*x)+rnorm(10,sd=.001)
  f()
  Error in eval(expr, envir, enclos) : couldn't find function "g"

Argh...]]

This is the same phenomenon that is documented for lattice graphics and
for lme in my notes on nonstandard evaluation rules.  I think it *is* a
bug.