Message-ID: <Pine.LNX.4.44.0306191349010.14814-100000@gannet.stats>
Date: 2003-06-19T12:54:10Z
From: Brian Ripley
Subject: Grouping binary data
In-Reply-To: <5.2.1.1.0.20030619131554.03715238@pop3.norton.antivirus>
On Thu, 19 Jun 2003, Henric Nilsson wrote:
> Dear all,
>
> I'm analyzing a binary outcome using glm() with a binomial distribution and
> a logit link, and have now reached the point where I'd like to do some
> model checking. Since my data are in binary form I'd like to collapse over
> the cross-classification of the factors before the model checking.
>
> Are there any nice and simple ways doing this? If so, how? If not, I'd be
> grateful for receiving some hints on how this can be accomplished.
Look at loglm1.data.frame in package MASS, or xtabs: each work by setting
up a suitable call to table.
If you want to sum up over cases with the same factors (not what is
usually meant by collapsing), take a look at multinom (package nnet) which
has options to do this for multinomials (and Bernoulli is a special case).
--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595