pairs( ) plot question

["Paul, David A" <paulda@BATTELLE.ORG>]

I have a factor variable f1 which I would like to
use to get pairs( ) to plot subsets of the specified
data.frame in various colors/symbols.

I am aware that panel = function(x,y) {  } can be used
to modify the pairs( ) plots... my naïve way to try to take
advantage of this was

pairs
(
        data = foo.frame, 
        panel=function(x,y) 
        {
                if( x != foo.frame$f1 & y != foo.frame$f1 )
                {
                        if( foo.frame$f1 == 1 )
                        {
                                col = 1;
                                points(x,y); 
                        }
                        else
                        {
                                col = 2;
                                points(x,y);
                        }
                }
        } 
)


This failed to work in spectacular fashion.  Obviously, I
want to exclude f1 from the points(x,y) calls since I don't
care to create panels for f1.  If someone would kindly 
point me in the right direction, I would be most grateful.


Much thanks in advance,

  david paul