Thanks all for the reply, I think what Bert specified is what I wanted. Thanks very much. So this model allows different random intercept term but the same random slope term for the three methods.
I have an additional question. I would like to require differnt residual variance also for the three groups. Is that possible? Thanks!! 2015-06-09 17:25 GMT-04:00, Bert Gunter <bgunter.4...@gmail.com>: > Thierry: > > I don't think so. It looks to me like her syntax/understanding is confused. > I think the call should be: > > mod2 <- lmer(result ~ group*time+(group + time|lot), na.action=na.omit, > data=alldata) > > Her request for "the same random slope for each group" -- I assume it's for > time -- means to me that the time slope will vary "randomly" by lot only, > the slope would be the same for all groups within the lot. > > Of course, I may be wrong also. If so, I suggest that she follow the > posting guide and post at least head(alldata) using dput() to enable folks > to understand the structure of her data. And only on r-sig-mixed-models -- > crossposting is frowned upon here and the mixed models list is the best bet > for this sort of question anyway. > > As always, corrections and criticism welcome. > > Cheers, > Bert > > Bert Gunter > > "Data is not information. Information is not knowledge. And knowledge is > certainly not wisdom." > -- Clifford Stoll > > On Tue, Jun 9, 2015 at 1:49 PM, Thierry Onkelinx <thierry.onkel...@inbo.be> > wrote: > >> Your model is too complex for the data. This gives you two options: a) >> simplify the model and b) get more data. >> >> Best regards, >> >> ir. Thierry Onkelinx >> Instituut voor natuur- en bosonderzoek / Research Institute for Nature >> and >> Forest >> team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance >> Kliniekstraat 25 >> 1070 Anderlecht >> Belgium >> >> 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 >> >> 2015-06-09 21:57 GMT+02:00 li li <hannah....@gmail.com>: >> >> > Hi all, >> > I'd like to fit a random intercept and random slope model. In my >> > data, there are three groups. I want to have different random >> > intercept for each group but the same random slope effect for all >> > three groups. I used the following R command. >> > However, there seems to be some problem. Any suggestions? >> > >> > >> > >> > mod2 <- lmer(result ~ group*time+(0+group1+ group2 + >> > group3+time|lot), na.action=na.omit, data=alldata) >> > >> > > summary(mod2) >> > Model is not identifiable... >> > summary from lme4 is returned >> > some computational error has occurred in lmerTest >> > Linear mixed model fit by REML ['merModLmerTest'] >> > Formula: result ~ group * time + (0 + group1 + group2 + group3 + time | >> > lot) >> > Data: alldata >> > >> > REML criterion at convergence: 807.9 >> > >> > Scaled residuals: >> > Min 1Q Median 3Q Max >> > -3.0112 -0.3364 0.0425 0.2903 3.2017 >> > >> > Random effects: >> > Groups Name Variance Std.Dev. Corr >> > lot group1 0.00000 0.000 >> > group2 86.20156 9.284 NaN >> > group3 55.91479 7.478 NaN 0.06 >> > time 0.02855 0.169 NaN -0.99 0.10 >> > Residual 39.91968 6.318 >> > Number of obs: 119, groups: lot, 15 >> > >> > Fixed effects: >> > Estimate Std. Error t value >> > (Intercept) 100.1566 2.5108 39.89 >> > group group2 -2.9707 3.7490 -0.79 >> > group group3 -0.0717 2.8144 -0.03 >> > time -0.1346 0.1780 -0.76 >> > group group2 :time 0.1450 0.2939 0.49 >> > group group3:time 0.1663 0.2152 0.77 >> > >> > Warning messages: >> > 1: In checkConv(attr(opt, "derivs"), opt$par, ctrl = control$checkConv, >> : >> > Model failed to converge with max|grad| = 0.147314 (tol = 0.002, >> > component 2) >> > 2: In checkConv(attr(opt, "derivs"), opt$par, ctrl = control$checkConv, >> : >> > Model failed to converge: degenerate Hessian with 2 negative >> eigenvalues >> > >> > ______________________________________________ >> > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >> > 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. >> > >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >> 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 -- To UNSUBSCRIBE and more, see 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.