[R-sig-eco] Using multiple species data for gam (Rajendra Mohan panda)

[Chris Howden]

I wonder, has anyone tried using a factor analysis on the species prior to
further analysis to remove the multicollinearity? It's a fairly common
method outside of ecology. I think the interpretation would be that each
factor represents a 'guild' of species (to borrow a term from the birders
out there).

Chris Howden B.Sc. (Hons) GStat.
Founding Partner
Data Analysis, Modelling and Training
Evidence Based Strategy/Policy Development, IP Commercialisation and
Innovation
(mobile) +61 (0) 410 689 945
(skype) chris.howden
chris at trickysolutions.com.au




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-----Original Message-----
From: R-sig-ecology [mailto:r-sig-ecology-bounces at r-project.org] On Behalf
Of David Warton
Sent: Thursday, 19 February 2015 9:37 AM
To: 'r-sig-ecology at r-project.org'
Subject: Re: [R-sig-eco] Using multiple species data for gam (Rajendra
Mohan panda)

Hi Rajendra,
I would not advise deleting species to get around issue with species
correlation, at least, not in most instances.  The species responses are
typically the responses of interest that you are trying to model so you
should not subset them to try and satisfy some assumption - the goal
should always be trying to change your model to fit the data, not changing
the data to fit the model.

As has been mentioned a few times before, the method to use to analyse
your data really depends on the analysis goal.  The research question
affects whether or not you need to worry about species correlation, and if
so, how to deal with it.

All the best
David



David Warton
Professor and Australian Research Council Future Fellow School of
Mathematics and Statistics and the Evolution & Ecology Research Centre The
University of New South Wales NSW 2052 AUSTRALIA phone (61)(2) 9385-7031
fax (61)(2) 9385-7123

http://www.eco-stats.unsw.edu.au/ecostats15.html



-----Original Message-----


Date: Wed, 18 Feb 2015 09:32:56 +0530

From: Rajendra Mohan panda
<rmp.iit.kgp at gmail.com<mailto:rmp.iit.kgp at gmail.com>>

Cc: "r-sig-ecology at r-project.org<mailto:r-sig-ecology at r-project.org>"
<r-sig-ecology at r-project.org<mailto:r-sig-ecology at r-project.org>>

Subject: Re: [R-sig-eco] Using multiple species data for gam

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Dear Prof David Warton



Thanks a lot for your nice introspection on my data. I appreciate your

valuable comments. I am also trying to explore gamm or VGAM to match its

suitability with data. Its fine. However, I am thinking to reduce my data

structure by removing some of the species showing interspecific

correlation. Honestly speaking I do not have thought of it. Can you please

give more insights regarding this (interspecies correlation). I am also

interested in studying species-environment relationship (not by CCA or
RDA).



Your kind comments are highly appreciated.





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