"Simon Pickett" <[EMAIL PROTECTED]> writes: > sure, thanks again.
What is the order of magnitude of newwt? If it is large and with a small variance, then the -1 correlation might be an artifact of extrapolating the individual lines to zero. Try centering newwt by subtracting its mean. > > summary(m2) > Linear mixed-effects model fit by REML > Formula: change.wt ~ newwt + (newwt | id) > Data: grow > AIC BIC logLik MLdeviance REMLdeviance > -6203.178 -6164.462 3107.589 -6239.374 -6215.178 > Random effects: > Groups Name Variance Std.Dev. Corr > id (Intercept) 1.0868e-02 0.1042482 > newwt 4.7069e-05 0.0068606 -1.000 > Residual 1.4236e-02 0.1193136 > # of obs: 4688, groups: id, 485 > > Fixed effects: > Estimate Std. Error DF t value Pr(>|t|) > (Intercept) 5.5692e-01 6.4189e-03 4686 86.761 < 2.2e-16 *** > newwt -3.2382e-02 4.5962e-04 4686 -70.455 < 2.2e-16 *** > --- > Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 > > Correlation of Fixed Effects: > (Intr) > newwt -0.954 > > > Can you provide the summary(m2) results? > > > >> -----Original Message----- > >> From: Simon Pickett [mailto:[EMAIL PROTECTED] > >> Sent: Wednesday, August 16, 2006 7:14 AM > >> To: Doran, Harold > >> Cc: r-help@stat.math.ethz.ch > >> Subject: [SPAM] - RE: [R] REML with random slopes and random > >> intercepts giving strange results - Bayesian Filter detected spam > >> > >> Hi again, > >> Even stranger is the fact that the coefficeints (the slope) > >> and the intercepts are not independent, in fact they are > >> directly inversely proportional (r squared = 1). > >> This means that that there isnt a random slope and intercept > >> for each individual (which is what I wanted), but straight > >> line that pivots in the middle and will change from > >> individual to individual. Is there a problem with the way I > >> have structured the random model or a deeper problem with lmer()? > >> here is the code I used > >> m2 <- lmer(changewt ~ newwt+(newwt|id), data = grow) > >> coef(m2) > >> Any suggestions very much appreciated, > >> Simon > >> > >> > >> > I don't this is because you are using REML. The BLUPs from a mixed > >> > model experience some shrinkage whereas the OLS estimates would not. > >> > > >> >> -----Original Message----- > >> >> From: [EMAIL PROTECTED] > >> >> [mailto:[EMAIL PROTECTED] On Behalf Of > >> Simon Pickett > >> >> Sent: Tuesday, August 15, 2006 11:34 AM > >> >> To: r-help@stat.math.ethz.ch > >> >> Subject: [R] REML with random slopes and random intercepts giving > >> >> strange results > >> >> > >> >> Hi everyone, > >> >> I have been using REML to derive intercepts and > >> coeficients for each > >> >> individual in a growth study. So the code is > >> >> m2 <- lmer(change.wt ~ newwt+(newwt|id), data = grow) > >> >> > >> >> Calling coef(model.lmer) gives a matrix with this > >> information which > >> >> is what I want. However, as a test I looked at each > >> individual on its > >> >> own and used a simple linear regression to obtain the same > >> >> information, then I compared the results. It looks like the REML > >> >> method doesnt seem to approximate the two parameters as > >> well as using > >> >> the simple linear regression on each individual > >> separately, as judged > >> >> by looking at graphs. > >> >> Indeed, why do the results differ at all? > >> >> Excuse my naivety if this is a silly question. > >> >> Thanks to everyone for replying to my previous questions, > >> very much > >> >> appreciated. > >> >> Simon Pickett > >> >> PhD student > >> >> Centre For Ecology and Conservation > >> >> Tremough Campus > >> >> University of Exeter in Cornwall > >> >> TR109EZ > >> >> Tel 01326371852 > >> >> > >> >> ______________________________________________ > >> >> 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. > >> >> > >> > > >> > >> > >> Simon Pickett > >> PhD student > >> Centre For Ecology and Conservation > >> Tremough Campus > >> University of Exeter in Cornwall > >> TR109EZ > >> Tel 01326371852 > >> > >> > > > > > Simon Pickett > PhD student > Centre For Ecology and Conservation > Tremough Campus > University of Exeter in Cornwall > TR109EZ > Tel 01326371852 > > ______________________________________________ > 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. > -- O__ ---- Peter Dalgaard Ă˜ster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907 ______________________________________________ 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.