R help - Oct 2011 - variable scope for deltavar function from emdbook

Dear all,

I want to use the deltavar() function from emdbook. I can use it 
directly from the command terminal but within a function it behaves weird.

Working example:
----------------------
library("emdbook")

fn <- function()
{
browser()
y <- 2
print(deltavar(y*b2, meanval=c(b2=3), Sigma=1) )
}

x <- 2
print(deltavar(x*b1, meanval=c(b1=3), Sigma=1) )
y<-3

fn()
------------------------

running this returns 4 for the first function call, which is fine.

For the call of deltavar in fn(), I get 9, i.e. the function uses y<-3 
instead of the local y<-2. If y<- is commented, deltavar returns an error.

So why is the function not using the local variable and how do I make it 
use it?

Many thanks

adad <adad <at> gmx.at> writes:
> Working example:
> ----------------------
> library("emdbook")
> 
> fn <- function()
> {
> browser()
> y <- 2
> print(deltavar(y*b2, meanval=c(b2=3), Sigma=1) )
> }
> 
> x <- 2
> print(deltavar(x*b1, meanval=c(b1=3), Sigma=1) )
> y<-3
> 
> fn()
> ------------------------
> 
> running this returns 4 for the first function call, which is fine.
> 
> For the call of deltavar in fn(), I get 9, i.e. the function uses y<-3 
> instead of the local y<-2. If y<- is commented, deltavar returns an
error.
> 
> So why is the function not using the local variable and how do I make it 
> use it?
  The real problem is that I (the author) don't understand scoping in R, and
how to manipulate it, as well as I'd like to. I will work on this (any
tips from the R-helpers appreciated).  In the meantime, you could
try out one of the other available delta-method calculators, such
as the one in the msm package (library("sos"); findFn("{delta
method}")).

  More text to try to make gmane happy

  Ben Bolker