Dear all,

I realised a correspondence analysis with function cca() of vegan library.
Just like in Okansen (2010) in the example of R help:

library(vegan)
data(varespec)
data(varechem)
vare.cca<-cca(varespec~ Al + P + K, varechem)

With plot.cca() function I represented the species matrix in the next way:
plot(vare.cca,display="species")

Being similar to:
plot((c(-2,2)),(c(-2,2)), type="n", xlab="AXIS 1", ylab="AXIS 2")
points(vare.cca,display='species')

Now, I want to add to this graph a standard error in 'x' and 'y' direction.
How can I add it? I tried different options but I do not get it. It will be
just like the function ordiellipse of ellipse library and others like
ordihull of vegan library, but without add any factor level. The program CAP
of Anderson realice this kind of output and I am wondering if in R exists
some function implemented that deals with it. Some examples of these
graphics will be found in Quero et al., 2008 Basic and Applied Ecology 9:
635-644; Maestre et al., 2009 Ecology Letters 12: 930 - 941.

Maybe I am looking for it in the wrong place. I would be grateful for any
help.

Thanks in advance,

Paloma

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