[R] 0-only-rows in correspondence analysis

Martin Wegmann mailinglist2_wegmann at web.de
Wed Oct 22 16:09:04 CEST 2003


Hello, 

I am looking for a workaround of "species empty" plots in a correspondence 
analysis. 

I tried to do a community structure analysis with a ca via decorana(), ca() 
and CAIV(), but none of them allow 0 only-rows.

I have species (abs./pres) in columns and sites in rows

	sp1 sp1 sp3 ...
plot1   0    1     1
plot2   0    0    0
plot3   1    0     1
.....

but on some plots no species could be found, therefore only 0 appear. I know 
that this isn't interesting for a community analysis but I am interested in 
the contributions of variables to the factors for a further analysis with 
env. variables where it is interesting that there are no species found. 

i thought about adding a "dummy" species with only presence on all sites, that 
would solve the 0-only-row problem but I am not sure if that would bias the 
outcome of a ca seriously.
 
Or is there a subcommand to allow 0 rows in a ca which I haven't seen?

thnaks Martin




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