That two distances are the same is *not* what the message says. You can't just look at elements of the results of dist() and simply relate them back to object numbers. Try as.matrix(x.dist) for a human-readable form.
On Fri, 1 Jun 2007, Thomas Zastrow wrote: > Dear all, > > I'm completely new to R and at first I must say that it is a great program! > > But I have a problem with the function isoMDS from the MASS package. I > have this code which I load with source() from a file: > > x <- c(163.59514923926784, 150.01448475257115, ...... {here are some > more values}) > x.sort <- sort(x) > x.dist <- dist(x.sort) > library(MASS) > x.mds <- isoMDS(x.dist) > plot(x.mds$points, type="n") > text(x.mds$points, labels=as.character("x")) > > The problem is in the line where the isoMDS function is applied: I got > the error: > > Fehler in isoMDS(x.dist) : zero or negative distance between objects 9 > and 10 > > When I look at values 8 and 9 of x.dist, I see that they have the same > values (I'm not wrong, it's values of 8 and 9 and not 9 and 10): > > x.dist[8:9] > [1] 39.8214 39.8214 > > So, just to give'm a try, I changed the value of x.dist[8]: > > x.dist[8] <- c(39.7) > > Now, there are defintitely different values in this part of x.dist: > > x.dist[7:10] > [1] 39.69898 39.70000 39.82140 39.98892 > > But when I start isoMDS again, I got again the error: > > x.mds <- isoMDS(x.dist) > Fehler in isoMDS(x.dist) : zero or negative distance between objects 9 > and 10 > > > So, where's my error? > > Thank you! > > Best, > > Tom > > > -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ 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 and provide commented, minimal, self-contained, reproducible code.