Joris De Wolf a écrit : > Have you tried to define 'an' as a group? Like in > > gls(IKAfox~an,correlation=corExp(2071,form=~x+y|an,nugget=1.22),data=renliev) > > > A small data set might help to explain the problem. > > Joris Thanks. Seems to work with a small artificial data set:
an<-as.factor(rep(2001:2004,each=10)) x<-rep(rnorm(10),times=4) y<-rep(rnorm(10),times=4) IKA<-rpois(40,2) site<-as.factor(rep(letters[1:10],times=4)) library(nlme) mod1<-gls(IKA~an-1,correlation=corExp(form=~x+y)) >Error in getCovariate.corSpatial(object, data = data) : Cannot have zero distances in "corSpatial" mod2<-gls(IKA~an-1,correlation=corExp(form=~x+y|an)) > mod2 Generalized least squares fit by REML Model: IKA ~ an - 1 Data: NULL Log-restricted-likelihood: -73.63998 Coefficients: an2001 an2002 an2003 an2004 1.987611 2.454520 2.429907 2.761011 Correlation Structure: Exponential spatial correlation Formula: ~x + y | an Parameter estimate(s): range 0.4304012 Degrees of freedom: 40 total; 36 residual Residual standard error: 1.746205 > > Joris > > Patrick Giraudoux wrote: >> Dear listers, >> >> I am trying to model the distribution of fox density over years in >> the Doubs department. Measurements have been taken on 470 plots in >> March each year and georeferenced. Average density is supposed to be >> different each year. >> >> In a first approach, I would like to use a general model of this >> type, taking spatial correlation into account: >> >> gls(IKAfox~an,correlation=corExp(2071,form=~x+y,nugget=1.22),data=renliev) >> >> >> but I get >> >> > >> gls(IKAfox~an,correlation=corExp(2071,form=~x+y,nugget=1.22),data=renliev) >> >> Error in getCovariate.corSpatial(object, data = data) : >> Cannot have zero distances in "corSpatial" >> >> I understand that the 470 geographical coordinates are repeated three >> times (measurement are taken each of the three years at the same >> place) which obviously cannot be handled there. >> >> Does anybody know a way to work around that except jittering slightly >> the geographical coordinates? >> >> Thanks in advance, >> >> Patrick >> >> ______________________________________________ >> 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 > > > confidentiality notice: > The information contained in this e-mail is confidential a...{{dropped}} ______________________________________________ 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