[R] Lattice::qqmath -- groups option question

Deepayan Sarkar deepayan at stat.wisc.edu
Thu Jun 10 16:54:36 CEST 2004

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.


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