Dear all,
I am trying to use Simpson dissimilarity measure (in Koelf et al 2003 JAE, as 
Beta Sim) to perform Nonmetric Multidimensional Scaling. 

First by making a dissimilarity matrix:

dis.mat <-betadiver(fine.scale, index = 22)
dis.mat<-as.matrix(dis.mat)

then using this matrix in meta MDS:
nms<-metaMDS(dis.mat,trymax=100,zerodist="add")

but I get this error:

Error in isoMDS(dist, k = k, trace = isotrace) : zero or negative distance 
between objects 5 and 6

checking my matrix, there is neither negative value or zero in my matrix.
So I am confused, where I am doing wrong.

Thank you very much for creating time and giving any hint.
Kind regards,
Omid

 




 Omid Paknia,
Institute of Experimental Ecology,
Albert-Einstein-Allee 11 
University of Ulm
D-89069 Ulm, 
Germany
http://www.uni-ulm.de/nawi/bio3/kalko/phdstud/paknia.html



      
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