[R] lme4 problem: model defining and effect estimation ------ question from new bird to R community from SAS community

[Dieter Menne]

Nilaya Sharma wrote:
> 
> I was trying to fit a mixed model in animal experiment but stuck at simple
> point. The following similar example is from SAS mixed model pp 212.
> 
> 
> genetic_evaluation <- read.table(textConnection("
> sire dam adg
> 1  1  2.24
> 1  1  1.85
> ...
> 5  2  2.58
> 5  2  2.56"), header = TRUE)
> 
> # my R practice codes
> require (lme4)
>  lmer(adg ~ 1 + (1|sire) + (1|dam/sire), data=genetic_evaluation)
> 
>  ****error message********************************************88
>  Error: length(f1) == length(f2) is not TRUE
> In addition: Warning messages:
> 

Thanks for providing a self-contained example. The error message is really a
bit confusing (anybody around who understands what lme thinks here?), but
the solution is simple. Just make sure that dam and sire are factors:

genetic_evaluation$dam = as.factor(genetic_evaluation$dam)
genetic_evaluation$sire = as.factor(genetic_evaluation$sire)

I recommend the excellent course notes in the MCMCglmm package as a
complementary reading.

Dieter




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