[R] Error message with nmds

From: Jonathan Hughes <jhughes_at_ess.washington.edu>
Date: Wed 17 May 2006 - 06:25:21 EST


I am trying to apply nmds to a data matrix but I receive the following error message:

Error in isoMDS(dis, y = y, k = k, maxit = maxit) :

        zero or negative distance between objects 5 and 7

The data are in a vegetation cover-class matrix (species in columns, plots in rows, classes 1-8 with lots of zero values) converted to a dissimilarity matrix (bray curtis).

I assumed that objects 5 and 7 refer to rows of my original data; and they do have the same species with the same cover classes. I deleted one of these rows but I received the same error message with a rerun of nmds. As it turns out, the new rows 5 and 7 are the same. How do I avoid this problem?

Any advice for this neophyte would be greatly appreciated. Thanks!



R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed May 17 06:30:30 2006

Archive maintained by Robert King, hosted by the discipline of statistics at the University of Newcastle, Australia.
Archive generated by hypermail 2.1.8, at Wed 17 May 2006 - 18:10:10 EST.

Mailing list information is available at https://stat.ethz.ch/mailman/listinfo/r-help. Please read the posting guide before posting to the list.