Lauren,

I am not aware of a single publication that uses 'goodness statistics' to 
remove species from ordination plots.  But that does not mean it is not common 
practice (just as failure to report nonsignificant results may be common 
practice...).

On another point, removing species from display (often a practical necessity) 
is very different from removing a species from analysis (which, if the idea is 
to understand species composition, is often a shady proposition if not 
justifiable on a priori grounds).  I hope most authors will provide criteria 
for removing species from display, and if not, reviewers should be on guard.


--Mike

Michael W. Palmer, Regents Professor, Botany Department, Oklahoma State 
University
104 LSE Stillwater OK 74078 USA 405-744-7717 
LABORATORY FOR INNOVATIVE BIODIVERSITY RESEARCH AND ANALYSIS: 
http://ecology.okstate.edu/Libra/ 
Wildfuels Blog: http://cas.okstate.edu/debo/blogs/
OSU Botany: http://botany.okstate.edu/     
OSU Ecology: http://ecology.okstate.edu 


-----Original Message-----
From: Ecological Society of America: grants, jobs, news 
[mailto:[email protected]] On Behalf Of L Quinn
Sent: Monday, November 23, 2009 1:49 PM
To: [email protected]
Subject: [ECOLOG-L] vegan package: goodness.cca function

Hello,

I am posting this to R-help and Ecolog-L, in hopes that enough Ecologgers are R 
users and enough R-help users are ecologists. Please forgive the cross-posting.

I deleted a number of species from a canonical correspondence analysis (CCA) 
model after using the function goodness.cca in vegan.  In his explanation of 
the diagnostic tools for CCA 
(http://cc.oulu.fi/~jarioksa/softhelp/vegan/html/goodness.cca.html), Jari 
Oksanen states that "It is a common practise to use goodness statistics to 
remove
species from ordination plots". However, I have not been able to find 
references on this "common practice" in the literature. I may be using 
inappropriate search terms?? However, if anybody can point me towards some 
cite-able references/rules of thumb on this, I would very much appreciate it.

And yes, I am also aware that Jari goes on to say that deleting species isn't 
always a good idea. 

Thank you!

Lauren Quinn
                                          
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