[R] [OT] correspondence analysis w/ non-mutually-exclusive categories

[Timothy Bock]

> My question is about the substance of correspondence
> analysis. Specifically, is it appropriate to use ca on a matrix of values
> such that the columns and/or rows are not mutually exclusive?

Correspondence analysis is applied extremely frequently to data with rows
and columns that are not mutually exclusive.  In market research, for
example, brand-attribute matrices are created of the form:

		Reliable	Fast	Sexy
Ford		25		35	40
Honda		50		28	100
Toyota	21		25	21

and correspondence analysis is then applied to create positioning maps.
There may be some theoretical reason why this is not sound, but practical
experience suggests it is very useful.  Of course, traditional approaches to
statistical inference on such maps - such as confidence intervals - become
inappropriate.

> - I am aware of the multiple correspondence technique, which I believe
> answers (some of) this issue. However I have a different problem with
> it: I have so many observations (ca. 5700) that the plot becomes
> unreadable. That's because each *observation* is plotted in mca, whereas
> each unique profile is what's plotted in ca.

I'm not sure how you're doing MCA, but it can certainly be done without
plotting each observation.  From memory, there is a good description of how
to do it in

Greenacre, Michael and Blasius, Jorg 1994 (eds.) Correspondence Analysis in
the Social Sciences. Recent Developments and Applications. London: Academic
Press.

Tim
>
> Any advice will be met with tremendous gratitude :)
>
> Andy Perrin
>
> ----------------------------------------------------------------------
> Andrew J Perrin - Ph.D. Candidate, UC Berkeley, Dept. of Sociology
> Chapel Hill, North Carolina, USA - http://demog.berkeley.edu/~aperrin
>         aperrin at socrates.berkeley.edu - aperrin at igc.apc.org
>
> -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.
> -.-.-.-.-.-.-
> r-help mailing list -- Read
> http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
> Send "info", "help", or "[un]subscribe"
> (in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
> _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._.
> _._._._._._._
>

-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._