Dear Luciano, The "1" in (1|NestID) indicates only a random intercept. Note that in most models in R, a "1" on the righthandside of the formula indicates the intercept, "-1" or "0" indicates no intercept. ~X, which is equivalent to ~X + 1, indicates a slope along X and an intercept. Hence a random slope and intercept is write as (X|NestID). If you only want the random slope then write (X + 0|Nest).
Note that (X|NestID) implies that the random slope and the random intercept can be correlated. If you need them to be independent you will have to write (X + 0|NestID) + (1|NestID). HTH, Thierry PS Next time try to send questions about lmer to the R-sig-mixed-models mailinglist. ------------------------------------------------------------------------ ---- ir. Thierry Onkelinx Instituut voor natuur- en bosonderzoek / Research Institute for Nature and Forest Cel biometrie, methodologie en kwaliteitszorg / Section biometrics, methodology and quality assurance Gaverstraat 4 9500 Geraardsbergen Belgium tel. + 32 54/436 185 thierry.onkel...@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-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] Namens Luciano La Sala Verzonden: woensdag 17 december 2008 15:47 Aan: r help Onderwerp: [R] Model building using lmer Dear R-experts, Quite new to R on this end, but learning fast (I hope). I am running version 2.7.1 on Windows Vista. I have small dataset which consists of: # NestID: nest indicator for each chicken. Siblings sharing the same nest have the same nest indicator. # Chick: chick indicator consisting of a unique ID for each single chick. # Year: 1, 2. # ClutchSize: 1-, 2- , 3-eggs. # HO: hatching order within each clutch (1, 2, 3 [first, second and third-hatched chick]). # SibComp: sibling competence: present/ absent (0, 1) # Death2: death at two days post-hatch (0, 1) # Death10: death at ten days post-hatch (0, 1) So a subset of my dataset looks something like this: NestID Chick Year ClutchSize HO Hatching SibComp Death2 Death10 1 1 1 1 1 1 1 1 1 2 2 1 1 1 1 1 0 0 3 3 1 1 1 0 0 0 0 4 4 1 1 1 1 0 1 0 4 5 1 2 2 0 1 0 1 5 6 1 2 1 1 0 0 0 5 7 1 2 2 0 0 0 0 6 8 2 3 1 1 1 0 0 6 9 2 3 2 1 0 1 0 6 10 2 3 3 0 1 0 0 7 11 2 3 1 0 0 0 1 7 11 2 3 2 0 0 0 0 7 11 2 3 3 1 1 1 1 ............ In order to account for lack of independence at the nest level (many chicks are siblings), I'd like to run a GLMM with random slopes and intercepts for nests. Using lmer, my model for survival at 10 days, for example, would read as follows (or not!): > model <- lmer(Death10 ~ HO + ClutchSize + SibComp + Year + (1|NestID), family=binomial, 1) > summary(model) >From what I understand, the model above includes only random intercepts for NestID. So at this point my question is how do I make this model into one which includes both random intercepts and slopes for NestID? Look forward to receiving your input. Thank you all for your time! Luciano ______________________________________________ R-help@r-project.org 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. 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. ______________________________________________ R-help@r-project.org 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.
