[R] canonical correspondence analysis

[Stephane Dray]

Canonical Correspondence Analysis is an ordination method widely used 
among ecologists (ter Braak). This method allow to analyze two tables 
(L and E) which have the same number of rows. It is a correspondence 
analysis of table L with linear constraint from E (multiple linear 
regression) : the row score are linear combination of variables of E. 
The columns scores are obtained by weighting averaging. CCA finds 
linear combination of external variables (E) to obtain a row score 
which maximizes the between-variance of columns score (obtained by 
averaging) . Ter Braak called it "canonical" correspondence analysis 
because it analyses two tables (like canonical analysis) but we 
preferred the more explicit name of correspondence analysis with 
respect to instrumental variables".
But .... in a theoretical point of view, CCA could be considered as a 
canonical correlation analysis (the same links as between 
correspondence analysis and canonical correlation analysis). I m just 
writing a R function to perform Correspondence analysis with or 
without linear contstraints (CA, CCA on row or column, Double CCA on 
rows and columns) and to make the graphical representation (bi or 
triplot).
I will be happy to communicate this function to anyone which is intersted in.

Sincerly,
-- 
Stéphane DRAY
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Biométrie et Biologie évolutive - Equipe "Écologie Statistique"
Universite Lyon 1 - Bat 711 - 69622 Villeurbanne CEDEX - France

Tel : 04 72 43 27 56			   Fax : 04 78 89 27 19
       04 72 43 27 57 	   E-mail : dray at biomserv.univ-lyon1.fr 
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ADE-4               http://pbil.univ-lyon1.fr/ADE-4/ADE-4F.html
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