Hello everyone,

 

I'm working with R 2.4.1 on a PC running with XP.

 

Trying to run isoMDS as follows:

 

Gquad.mat <- Gquads[4:10]   # extracts only the metric data variables

Gquad.dist <- dist(Gquad.mat) 

Gquad.mds <- isoMDS(Gquad.dist)

plot(Gquad.mds$points, type = "n")

text(Gquad.mds$points, labels = as.character(Gquads$Quadname), cex = .5)

 

 

The data.frame includes 711 records, and the first 3 columns contain
categorical variables which I exclude from the analysis.

 

When I invoke the script above an error message is returned.

 

Error in isoMDS(Gquad.dist) : zero or negative distance between objects
179 and 180.

 

How can I handle this, is it valid to add 0.5 to every element in the
distance matrix or is someother  alternative more appropriate?

 

Thanks in advance

Steve

 

 

Steve Friedman, PhD

Everglades Division

Senior Environmental Scientist, Landscape Ecology

South Florida Water Management District

3301 Gun Club Road

West Palm Beach, Florida 33406

email:  sfriedma@sfwmd.gov

Office:  561 - 682 - 6312

Fax:      561 - 682 - 5980

 

If you are not doing what you truly enjoy its your obligation to
yourself to change.

 


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