Trended Correspondence Analysis

James F Gilliam jfgzo at
Sat Jan 22 16:06:54 EST 1994

Peter D. Wilson (peter at wrote:
: Posting for a friend:

: I have been asked to trace some software which performs 
: "Trended Correspondence Analysis". It is to be used in botany and is  
: believed to have been created by a botanist. Any help would be  
: appreciated.

: - peter
: -- 
: peter d. wilson                                                         
: email: peter at  (NeXTMail OK)            
: Voice: (403) 283-9743  Fax: (403) 283-0036                            
:      Independent NextStep Developer                                           

Before using Detrended Correspondence Analysis, you might 
want to read 
James, FC and CE McCulloch, 1990, Multivariate analysis in ecology and 
systematics: panacea or Pandora's box? Annual Reviews of Ecology and 
Systematics 21:129-166.  

For what it's worth, I recently looked at DCA and some other multivariate 
analyses for a particular ecological use, and decided to use the good ol' 
principal components (PCA) and factor analysis after all.  DCA is intended 
to improve upon the PCA, but carries with it some new problems (see James 
and McCulloch).  Given 
that neither technique is a 'magic bullet,' it might be just as well to 
stick with PCA, as it is more familiar, and most stat programs do it 
(SAS, SPSS, at least).  DCA might (or might not) be discarded in ten 
years, but PCA has a historical tradition and straightforward mathematics 
(just pulling out eigenvalues) which make it a likely candidate for 

Regardless of what you or, actually, your friend uses, don't expect 
miracles from any multivariate 
technique.  It will help you organize your data, but you are still going 
to need to wrack your brain to decide what it tells you that is useful, 
if anything at all.

Jim Gilliam
james_gilliam at (preferred) or jfgzo at
Department of Zoology
North Carolina State University
Raleigh, NC 27695-7617

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