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Behaviour of mle and environments or calling mle inside a function

2 messages · Iago Mosqueira, Brian Ripley

Original
Iago Mosqueira
# 
Dear all,

I would appreciate some help understanding the following behaviour
when stats4::mle is called inside a function. mle seems to look for
its arguments in R_GlobalEnv and not the environment from which it is
called.


library(stats4)

lkhd <- function(alpha=1, beta=0.1, sigma=0.1)
	- sum(dnorm(log(rec), log(alpha*ssb/(beta+ssb)), sqrt(sigma), TRUE))

object <- list(lkhd=lkhd, rec=1:10, ssb=1:10)

foo <- function(x)
{
	rec <- x$rec
	ssb <- x$ssb

	mle(x$lkhd)
}

foo(object)


This fails with

Error in log(rec) : object "rec" not found


rec <- object$rec
ssb <- object$ssb

foo(object)

and this works.

Using R version 2.5.0 (2007-04-23), on Linux (Ubuntu) 2.6.17

Many thanks,


Iago Mosqueira
Brian Ripley
#
On Tue, 26 Jun 2007, Iago Mosqueira wrote:

            

      
      
      
    

        
It is your function lkhd() that is doing the looking, and lexical scoping 
means that it should be looking in .GlobalEnv (sic), since that is where 
you defined it.  Try a traceback:

            

      
      
      
    

        
10: log(rec)
9: dnorm(log(rec), log(alpha * ssb/(beta + ssb)), sqrt(sigma), TRUE)
8: sum(dnorm(log(rec), log(alpha * ssb/(beta + ssb)), sqrt(sigma),
        TRUE))
7: minuslogl(alpha = 1, beta = 0.1, sigma = 0.1)
6: do.call("minuslogl", l)
5: fn(par, ...)
4: function (par)
    fn(par, ...)(c(1, 0.1, 0.1))
3: optim(start, f, method = method, hessian = TRUE, ...)
2: mle(x$lkhd)
1: foo(object)

I am afraid I have no idea why you thought that your function would look 
in the body of foo().