Hello I'm trying to specify a mixed-effect model describing "unmet NEED" (of families with disabled children) as a function of IMPAIRMENT (i.e. intrinsic severity of the child's condition) and AREA of residence (factor with ~15 levels). The impairment measure is a unidimensional variable but it needs "calibrating" for separate types of disability (autism, cerebral palsy etc) represented by another factor, DISCAT In lmer syntax I have NEED ~ IMPAIRMENT | DISCAT + 1 | AREA but I want to specify independence of random effects. I'm aware of the pdDiag options in the nlme library but unsure how to specify the model in lme syntax? Thank you Rob
specifying independence of random effects?
2 messages · Rob Forsyth, ONKELINX, Thierry
Dear Rob, I suppose that IMPAIRMENT is a continunous variable. In that case you can use (IMPAIRMENT - 1|DISCAT) + (1 |DISCAT) to indicate that the random intercept and the random slope are independent. AFAIK you can only specify a full variance-covariance matrix between random effects or independent random effects. So structures like pdIdent, pdCompSymm, ... are not available in lme4. HTH, Thierry ------------------------------------------------------------------------ ---- ir. Thierry Onkelinx Instituut voor natuur- en bosonderzoek team Biometrie & Kwaliteitszorg Gaverstraat 4 9500 Geraardsbergen Belgium Research Institute for Nature and Forest team Biometrics & Quality Assurance Gaverstraat 4 9500 Geraardsbergen Belgium tel. + 32 54/436 185 Thierry.Onkelinx at inbo.be 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: r-sig-mixed-models-bounces at r-project.org [mailto:r-sig-mixed-models-bounces at r-project.org] Namens Rob Forsyth Verzonden: donderdag 10 december 2009 17:31 Aan: r-sig-mixed-models at r-project.org Onderwerp: [R-sig-ME] specifying independence of random effects? Hello I'm trying to specify a mixed-effect model describing "unmet NEED" (of families with disabled children) as a function of IMPAIRMENT (i.e. intrinsic severity of the child's condition) and AREA of residence (factor with ~15 levels). The impairment measure is a unidimensional variable but it needs "calibrating" for separate types of disability (autism, cerebral palsy etc) represented by another factor, DISCAT In lmer syntax I have NEED ~ IMPAIRMENT | DISCAT + 1 | AREA but I want to specify independence of random effects. I'm aware of the pdDiag options in the nlme library but unsure how to specify the model in lme syntax? Thank you Rob _______________________________________________ R-sig-mixed-models at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models Druk dit bericht a.u.b. niet onnodig af. Please do not print this message unnecessarily. Dit bericht en eventuele bijlagen geven enkel de visie van de schrijver weer en binden het INBO onder geen enkel beding, zolang dit bericht niet bevestigd is door een geldig ondertekend document. The views expressed in this message and any annex are purely those of the writer and may not be regarded as stating an official position of INBO, as long as the message is not confirmed by a duly signed document.