NMDS for biomass

I would like to make a NMDS with biomass of different prey groups in stomach content of fish.

I have already made one where the data matrix consists of 0 and 1, and this one went fine but are not able to do it when adding the actual weights.

I have used the MASS and vegan package. When using binomial data matrix:

mymetaMDS <- metaMDS(comm, distance = "jaccard", na.rm = TRUE, binomial = TRUE)


and this works fine.

But when I try to create the dissimilarity matrix with the weight data matrix:

mymetaMDS <- metaMDS(comm, distance = "jaccard", na.rm = TRUE, binomial = FALSE)


Error in if (any(dist < -sqrt(.Machine\$double.eps))) warning("some dissimilarities are negative -- is this intentional?") : missing value where TRUE/FALSE needed In addition: Warning messages: 1: In distfun(comm, method = distance, ...) : you have empty rows: their dissimilarities may be meaningless in method "jaccard" 2: In distfun(comm, method = distance, ...) : missing values in results

Any suggestions any one?

• Why apply non-metric methods to measured data? More generally, it is best to assume ignorance of biology when posting here. People don't necessarily know how biomass is measured. – Nick Cox Feb 6 '14 at 17:29