Re: [R] 'with' usage question

[Roger D. Peng]

I think what's happening is that the function aov.SS1 will look up 
variables in the environment in which it was *defined*, which in your 
case (I'm guessing) is the global environment/workspace.  Therefore, 
if `speed' and `Subject' are not defined in the global environment, 
they will not be found.

-roger
RenE J.V. Bertin wrote:
Hello,
I'm having a little argument with the 'with' function. I have 

aov.SS1 <- function( y, indep=speed, fSnr=Subject, ... )
{
        indep <- factor(speed)
        fSnr <- factor(fSnr)
  ## ....
}
and a dataframe containing speed, Subject, and a bunch of other columns. If I now do

with( data, aov.SS1( y=Obs ) )

I get a message
Error in factor(indep) : Object "speed" not found
It seems that automatic argument initialisation doesn't work, as the only effectively 
valid call seems to be

with( data, aov.SS1( y=Obs, indep=speed, fSnr=Subject ) )

whereas

with( data, speed )

prints what one would expect (i.e. data$speed).
How come? From ?with, one learns that 
     "... assignments within 'expr' take place in the constructed
     environment and not in the user's workspace."

Which to me reads that a with statement as above is equivalent to

attach(data) ; aov.SS1(y=Obs) ; detach(data)

Or is that just wishful thinking??
RenE
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