Re: R-alpha: batch mode and interactions

Ross Ihaka (ihaka@stat.auckland.ac.nz)
Thu, 6 Jun 1996 12:37:53 +1200


Date: Thu, 6 Jun 1996 12:37:53 +1200
From: Ross Ihaka <ihaka@stat.auckland.ac.nz>
Message-Id: <199606060037.MAA07802@stat.auckland.ac.nz>
To: r-testers@stat.math.ethz.ch
Subject: Re: R-alpha: batch mode and interactions
In-Reply-To: <9606042333.AA23240@attunga.stats.adelaide.edu.au>
 <199606042316.LAA03075@stat.auckland.ac.nz>

Bill Venables writes:
 > Of course even this does not go far enough.  There are two types of
 > "interaction" between factors, the "A:B" type and the "B %in% A"
 > type which are equivalent in abstract terms to "B + A:B".  I think
 > labelling is potentially very important in this area but doing it
 > justice is going to generate labels far too long.  You can't win.

Oops.  I see that my previous message was perhaps somewhat orthogonal
to your message.  I was talking about term labels and you were
talking about parameter labels.  To get nesting information showing up
in parameter labels would require changing the result returned by
terms().  Variable labels are made up in model.matrix based on
information passed on from terms.  Unfortunately, the only information
on nesting passed on from terms() is in the terms labels.  It would be
pretty hard to pull these apart to get nesting info out.

	Ross
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