I'm trying to perform a mantel test that ignores specific pairs in my

distance matrices. The reasoning is that some geographic distances

below a certain threshold suffer from spatial autocorrelation, or

perhaps ecological relationships become less relevant that stochastic

processes above a certain threshold.

The problem is that I can't find a way to do it. If I replace values

in either or both of the distance matrices with NA, mantel.rtest (ade4

package) gives the following error: Error in if (any(distmat < tol))

warning("Zero distance(s)") : missing value where TRUE/FALSE needed

Here's a trivial example that tries to exclude elements of the first

matrix that equal 11:

library(ade4)

a <- matrix(data = 1:36, nrow = 6)

b <- matrix(data = 1:36, nrow = 6)

a[a==11] <- NA

mantel.rtest(as.dist(a), as.dist(b))

Is there a way to do this, either with this package or another?

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