[R] NA in cca (vegan)

[Kim Vanselow]

Dear all,
I would like to calculate a cca (package vegan) with species and environmental data. One of these environmental variables is cos(EXPOSURE).
The problem: for flat releves there is no exposure. The value is missing and I can't call it 0 as 0 stands for east and west.
The cca does not run with missing values. What can I do to make vegan cca ignoring these missing values?
Thanks a lot,
Kim

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