R help - Jun 2004 - Lattice::qqmath -- groups option question

Does the 'groups' option on qqmath just color the points differently in
the main distribution or does it actually overlay separate quantile plots for
each subset? I would like to be able to do the latter.

--Rich

Richard Kittler 
AMD TDG
408-749-4099

On Thursday 10 June 2004 09:21, richard.kittler at amd.com
wrote:
> Does the 'groups' option on qqmath just color the points
differently
> in the main distribution or does it actually overlay separate
> quantile plots for each subset? I would like to be able to do the
> latter.
The 'groups' option doesn't really do anything in any of the high
level
lattice functions, it just sends the groups variable (and associated 
subscripts) to the panel function. It is the panel function that needs 
to know how to deal with that information. 

As things stand now, panel.qqmath doesn't know what to do with it. More 
importantly, qqmath is currently structured in a way that would make 
this very difficult to implement.

I don't think there's a good reason for this (other than consistency 
with S-PLUS) and I would prefer to allow the possibility of grouped Q-Q 
plots. But this would need a fair bit of restructuring and will 
certainly not happen before R 2.0.0.

Deepayan

Thanks for the info. Given that I rule out qqmath would the best method be to
make repeated calls to qqnorm without plotting and then overlay the results or
is there a more elegant method?

--Rich

Richard Kittler 
AMD TDG
408-749-4099

-----Original Message-----
From: Deepayan Sarkar [mailto:deepayan at stat.wisc.edu] 
Sent: Thursday, June 10, 2004 7:55 AM
To: r-help at stat.math.ethz.ch
Cc: Kittler, Richard
Subject: Re: [R] Lattice::qqmath -- groups option question


On Thursday 10 June 2004 09:21, richard.kittler at amd.com
wrote:
> Does the 'groups' option on qqmath just color the points
differently
> in the main distribution or does it actually overlay separate quantile 
> plots for each subset? I would like to be able to do the latter.
The 'groups' option doesn't really do anything in any of the high
level
lattice functions, it just sends the groups variable (and associated 
subscripts) to the panel function. It is the panel function that needs 
to know how to deal with that information. 

As things stand now, panel.qqmath doesn't know what to do with it. More 
importantly, qqmath is currently structured in a way that would make 
this very difficult to implement.

I don't think there's a good reason for this (other than consistency 
with S-PLUS) and I would prefer to allow the possibility of grouped Q-Q 
plots. But this would need a fair bit of restructuring and will 
certainly not happen before R 2.0.0.

Deepayan