Generalised Procrustes Analysis and Grids?

Miguel Sottomayor (
Wed, 6 May 1998 16:54:05 +0100 (BST)

Hello to Everibody

I introduce myself a few months ago saying that I was trying to apply pcp
to the study of product (wine) choice perceptual maps and consumer's
Well, I'm now starting to analyse data from about 60 grids ranging from 3
to 25 constructs (ratings 1 to 7).
Amonst other things I'm using Generalized Procrustes Analysis (GPA) as a
way to reach "aggregated" perceptual maps for pre-defined groups of
respondents (on the basis of several background variables) and doing
so trying to identify different perceptual segments.

Three major problems are allways coming to my mind:

1 - How to validate the interpretation of the "aggregated constructs" or
factors that are produced by GPA (a list of "real" constructs
highly correlated with each factor is given by GPA and is the basis of
my interpretation..);

2 - How sure can I be about the differences on perceptual spaces?

3 - Is the method consistent with the PCP theory?

I wonder if somebody have used GPA before for rep.grid analysis and can
help me with suggestions. I'm using Genstat which is not particularly user
friendly.. Are there other packages with GPA on it?

I'm not familiar with any other method dealing statistically with
"averaging" grids within groups.. Is anybody able to give me suggestions?

I would appreciate if anybody can help me with this...


P.S. For the ones interested I would suggest as
a very good first introduction to GPA:

Dijksterhuis, G.B. + Gower, J.C (1991)
The Interpretation of Generalized Procrustes Analysis and Allied
Methods. Food Quality and Preferences, 3(2), pp.67-87

Miguel L. Sottomayor
PhD Student - Dept. Agricultural and Food Economics
University of Reading, 4 Earley Gate
Whiteknights Rd, Reading
Tel +(0)118 9875 123 (ext 7703) Fax +(0)118 9756 467
Home Tel +(0)118 9662795
Home Adress: 17 Southlake Court, Bodmin Road
Woodley, Berkshire RG5 3SQ (UK)