RE: [R] sample variogram construction
Matt, In this case you are plotting the variogram of the residuals of the lme object, not of the data themselves. In your model you are assuming a linear relationship between count and time, with different intercepts and slopes for your different individuals. You are also assuming that the residuals exhibit stationarity. The Variogram function *should* work, so I can only suggest that there is something wrong with your data or code. Mixed-Effects Models in S and S-Plus by Pinheiro and Bates will probably help. Dan Department of Plant Sciences University of Oxford South Parks Road Oxford OX1 3RB UK Tel. 01865 275000 -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: 25 October 2004 18:32 To: [EMAIL PROTECTED]; [EMAIL PROTECTED] Subject: RE: [R] sample variogram construction Okay thanks! No I have the following difficulty implementing a variogram in the nlme package: cd1 - lme(count ~ time, data=cd4,random= ~ time | id) plot(Variogram(cd1, form= ~ time | id, robust=TRUE)) Error in as.array(X) : attempt to set an attribute on NULL Im not sure how to fix this, and apply this function to a longitudinal data with unequal times? Any help would be appreciated Quoting Dan Bebber [EMAIL PROTECTED]: Hi Matt, there are several R packages that will compute the sample variogram for you. Check out GeoR, sgeostat, nlme, spatial. There's no point in recoding the whole lot yourself, unless as a learning excercise. D p.s. For time series autocorrelations, you could use acf in package stats. Message: 9 Date: Mon, 25 Oct 2004 02:02:06 -0400 From: [EMAIL PROTECTED] Subject: [R] sample variogram construction To: [EMAIL PROTECTED] Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=US-ASCII Hi Im attempting to build a sample variogram for 300 obersvations of longitudinal data. So what I need to do is compute the half squared differences between pairs of residuals (for instance if a subject has 4 obersvations, this is 4 choose 2 paird differences) for each subject. Also, then I need the corresponding time differences within each individual. So the end result will be a 300 by 2 matrix with columns corresponding to paired difference residuals within subject and time differences within subject. Basically im having trouble coding this kind of matrix in R, if anyone can help me out or give me some tips id appreciate it. Thanks. Stuck in the for loop student __ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
RE: [R] sample variogram construction
Hi Matt, there are several R packages that will compute the sample variogram for you. Check out GeoR, sgeostat, nlme, spatial. There's no point in recoding the whole lot yourself, unless as a learning excercise. D p.s. For time series autocorrelations, you could use acf in package stats. Message: 9 Date: Mon, 25 Oct 2004 02:02:06 -0400 From: [EMAIL PROTECTED] Subject: [R] sample variogram construction To: [EMAIL PROTECTED] Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=US-ASCII Hi Im attempting to build a sample variogram for 300 obersvations of longitudinal data. So what I need to do is compute the half squared differences between pairs of residuals (for instance if a subject has 4 obersvations, this is 4 choose 2 paird differences) for each subject. Also, then I need the corresponding time differences within each individual. So the end result will be a 300 by 2 matrix with columns corresponding to paired difference residuals within subject and time differences within subject. Basically im having trouble coding this kind of matrix in R, if anyone can help me out or give me some tips id appreciate it. Thanks. Stuck in the for loop student __ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
RE: [R] sample variogram construction
Okay thanks! No I have the following difficulty implementing a variogram in the nlme package: cd1 - lme(count ~ time, data=cd4,random= ~ time | id) plot(Variogram(cd1, form= ~ time | id, robust=TRUE)) Error in as.array(X) : attempt to set an attribute on NULL Im not sure how to fix this, and apply this function to a longitudinal data with unequal times? Any help would be appreciated Quoting Dan Bebber [EMAIL PROTECTED]: Hi Matt, there are several R packages that will compute the sample variogram for you. Check out GeoR, sgeostat, nlme, spatial. There's no point in recoding the whole lot yourself, unless as a learning excercise. D p.s. For time series autocorrelations, you could use acf in package stats. Message: 9 Date: Mon, 25 Oct 2004 02:02:06 -0400 From: [EMAIL PROTECTED] Subject: [R] sample variogram construction To: [EMAIL PROTECTED] Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=US-ASCII Hi Im attempting to build a sample variogram for 300 obersvations of longitudinal data. So what I need to do is compute the half squared differences between pairs of residuals (for instance if a subject has 4 obersvations, this is 4 choose 2 paird differences) for each subject. Also, then I need the corresponding time differences within each individual. So the end result will be a 300 by 2 matrix with columns corresponding to paired difference residuals within subject and time differences within subject. Basically im having trouble coding this kind of matrix in R, if anyone can help me out or give me some tips id appreciate it. Thanks. Stuck in the for loop student __ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
