Emma, It looks like there is at least one location that has been sampled at least twice in some year. A co-worker of me got similar errors. After checking his data carefully he found a duplicate row. Removing the duplicate row solved his problem.
HTH, Thierry ------------------------------------------------------------------------ ---- ir. Thierry Onkelinx Instituut voor natuur- en bosonderzoek / Research Institute for Nature and Forest Cel biometrie, methodologie en kwaliteitszorg / Section biometrics, methodology and quality assurance Gaverstraat 4 9500 Geraardsbergen Belgium tel. + 32 54/436 185 [EMAIL PROTECTED] www.inbo.be To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of. ~ Sir Ronald Aylmer Fisher The plural of anecdote is not data. ~ Roger Brinner The combination of some data and an aching desire for an answer does not ensure that a reasonable answer can be extracted from a given body of data. ~ John Tukey -----Oorspronkelijk bericht----- Van: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Namens [EMAIL PROTECTED] Verzonden: woensdag 2 juli 2008 12:29 Aan: r-help@r-project.org Onderwerp: [R] Correlation structures in gls with repeated measurements Hi, I am trying include a spatial correlation structure into a gls model but keep getting the following error: > ocean<-read.table("C:\\oceanography2.txt",header=TRUE) > library(nlme) > YEAR<-as.factor(ocean$YEAR) >group<-groupedData(san_dens~temp_grad*pyc_grad*start_thermo|YEAR,data=o cean) > model1<-gls(san_dens~temp_grad*pyc_grad*start_thermo,data=group) > model2<-update(model1,corr=corSpher(form=~MIDLONGDEC+MIDLATDEC|YEAR)) Error in getCovariate.corSpatial(object, data = data) : Cannot have zero distances in "corSpatial" The measurements have been repeated over 10 years so the coordinates are repeated which I assume is the reason for this error. I thought grouping by YEAR should remove this but it doesnt seem to work, or I am making a mistake when I am trying to group it? I have noticed a couple of other posts with the same problem but I have still not managed to solve this. I would be really grateful if anyone has any ideas or has had this problem before. Thanks in advance, Emma Hazard ______________________________________________ R-help@r-project.org 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. ______________________________________________ R-help@r-project.org 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.