Hi all, I am trying to run a linear mixed effect models in lmer() from the lme4 package using the weights option.
I am using the R version 2.7.2 (2008-08-25) and lmer version in lme4_0.999375-26, which I think it is the latest version! I am getting and error message when I add the option "weights" in the lmer function. This is the error message I get "Error en mer_finalize(ans) : Calculated PWRSS for a LMM is negative". I have been reading in the last few weeks all the forum questions and answers about this issue. Certainly this has been discussed MANY times before especially with older versions of lmer (much less in the newer versions). I have been trying different things following peoples advice with not happy end, even I tried older version of lmer where the weight option was not giving an error message but it was not affecting the model at all, hoping maybe It did work some time in the past. This is an simple example of one of my models with varying intercept and slope. I am looking how the mean size of fish has been changing over time in different stocks. This is a simple model but it will get more complicated in the future. I just need to make the option of weights to work before the model becomes more complex. MODEL WITH NO WEIGHTS > M1<- lmer(meansize_scaled~year + (year |stock ), data=cas) # two levels > > M1 Linear mixed model fit by REML Formula: meansize_scaled ~ year + (year | stock) Data: cas AIC BIC logLik deviance REMLdev -2777 -2742 1395 -2807 -2789 Random effects: Groups Name Variance Std.Dev. Corr stock (Intercept) 1.0964e-02 0.1047097 year 3.2435e-06 0.0018010 -0.273 Residual 2.0193e-02 0.1421010 Number of obs: 2692, groups: stock, 9 Fixed effects: Estimate Std. Error t value (Intercept) 0.4869771 0.0360736 13.500 year 0.0001034 0.0006642 0.156 Correlation of Fixed Effects: (Intr) year -0.341 > MODEL WITH WEIGHTS. > M2<- lmer(meansize_scaled~year + (year |stock ), data=cas, weights=N_fish) # two level model Error en mer_finalize(ans) : Calculated PWRSS for a LMM is negative As you see above I get the message error. I read read read in the [R] and [R-sig-ME] and I did not get any clear solutions to the weight problem in lmer. My feeling is that the weight option in lmer just not work! At least at the present time, maybe in the future it will change. Can anybody share with me how they have deal with this issue? Should I give up with lmer and try to do this analysis using other tools? maybe try to learn the function lme from nlme package? I just would like to know if I need to give up with weight option in lmer or if I am missing something obvious but I did not find it yet. I want to emphasize that I really appreciate all the hard work of everybody (specially Douglas Bates) for always working hard answering everybody´s questions and improving the lmer function!! SincerelyMaria >))):) >))):) >))):) >))):) >))):) >))):) >))):) >))):) Maria Jose Juan Jorda Phd Student AZTI - Tecnalia / Unidad de Investigación Marina Herrera Kaia Portualde z/g 20110 Pasaia, Gipuzkoa, Spain Recursos Marinos y Pesquerias Depart. Biologia Animal, Vegetal y Ecologia Universidade A Coruña Campus A Zapateira s/n 15071, A Coruña, Spain Tel. +34981167000 ext. 2204 Fax. +34981167065 [EMAIL PROTECTED] _________________________________________________________________ [[elided Hotmail spam]] [[alternative HTML version deleted]]
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