[R] vegan -varpart is bigger than 100% in total?

Jari Oksanen jari.oksanen at oulu.fi
Thu May 2 08:17:16 CEST 2013

Ozgul Inceoglu <Ozgul.Inceoglu <at> ulb.ac.be> writes:

> I am trying to find the percentage of the parameters explaining the
bacterial community composition. I
> have one data matrix with relative abundance of OTUs and one with
environmental parameters. I used
> varpart in vegan package but the values in the venn diagram is bigger than
100% in total.How is it possible?

Dear Ozgul Inceoglu,

This is not possible and this is not the case. What is possible, and
what does happen is that you can have negative components in your
diagram. These negative components are mind boggling, but they do
appear regularly. Legendre & Legendre (2012) "Numerical Ecology" give
some reasons for their occurrence.

In you Venn diagram you have obviously selected an option of not 
displaying negative terms. Get the full sums of the components,
including negative ones, and I bet the sums will match.

Cheers, Jari Oksanen

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