Hi Gabriel,
for your poll: I am principally against, but practically in favour of
your suggestion.
Here's why:
Grouping (categorising) things inevitably looses information you may
want to keep when comparing species and environment. Personally, I try
to follow Frank Harrell's advice (which was on his earlier homepage, now
sadly scrapped): "Avoid, at all costs, the categorization of continuous
variables."
Having said that, your question is somewhat incomplete. What happens
with the clusters? How will they be represented in the next step?
Through the first axis of a PCA for each cluster? By one of the cluster
members?
If there was a clear ecological reason to select one variable from a
cluster over all others then I would be prepared to find clustering a
useful step (one that I in fact frequently use).
As always, context may dictate the approach.
Cheers,
Carsten
On 22.02.11 23:24, gabriel singer wrote:
Hi list,
Conducting sort of an opinion poll among list members.
Start with two matrices, one environmental, one species, same sites. I
wondered what people think of defining groups by a cluster analysis
based on the environmental variables (say, hclust or similar). Then
testing for a difference among those groups with regard to the second
species data set (say, adonis or mrpp).
I guess the spatial people will feel hurt at least? The strategy seems
to be quite common, though. Would be nice to hear opinions.
cheers, gabriel
_______________________________________________
R-sig-ecology mailing list
R-sig-ecology@r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
--
Dr. Carsten F. Dormann
Department of Computational Landscape Ecology
Helmholtz Centre for Environmental Research-UFZ
(Department Landschaftsökologie)
(Helmholtz Zentrum für Umweltforschung - UFZ)
Permoserstr. 15
04318 Leipzig
Germany
Tel: ++49(0)341 2351946
Fax: ++49(0)341 2351939
Email: carsten.dorm...@ufz.de
internet: http://www.ufz.de/index.php?de=4205
Registered Office/Sitz der Gesellschaft: Leipzig
Commercial Register Number/Registergericht: Amtsgericht Leipzig,
Handelsregister Nr. B 4703
Chairman of the Supervisory Board/Vorsitzender des Aufsichtsrats: MinR
Wilfried Kraus
Scientific Managing Director/Wissenschaftlicher Geschäftsführer: Prof.
Dr. Georg Teutsch
Administrative Managing Director/Administrativer Geschäftsführer: Dr.
Andreas Schmidt
_______________________________________________
R-sig-ecology mailing list
R-sig-ecology@r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
