[R-sig-ME] Error en mer_finalize(ans) : Downdated X'X is not positive definite, 1. What is wrong with my model?

[PALACIO BLASCO, SARA]

Dear Ben,

Thanks for your response. I had read a very similar response to FAQs  
explaining why the error relates to rank deficient models. I have  
tried to center Treatment (a continuous variable, sorry I didn't  
specify this!) but this does not remove the error.

I think the problem comes with the nested nature of "Species" within  
"Bud_type", since not all species are in all Bud_types, I have a rank  
deficient design and lme4 cannot cope with it. I  do not think there  
is a solution to this problem other than including "Species" as a  
random effect, but then I will not be able to know its effect...

Cheers,

Sara Palacio

Quoting Ben Bolker <bbolker at gmail.com>:

> PALACIO BLASCO, SARA <s.palacio at ...> writes:
>
> [snip]
>
>> I am trying to run the following model in glmer:
>>
>> > M_bud_type1=glmer(Dead~Treatment* fBud_type + fBud_type:Species +
>> > (1|fRep), family=binomial, data=species)
>>
>> where:
>> - Dead is a binomial response variable
>> - fBud_type is a fixed factor with 3 levels
>> - Species is a fixed factor with 9 levels nested within fBud_type and
>> - fRep is a random factor with 27 levels nested within Species
>>
>> I have 1386 observations.
>> The error message I receive reads:
>>
>> Error en mer_finalize(ans) : Downdated X'X is not positive definite, 1.
>>
>
>   Did you already read the http://glmm.wikidot.com/faq#errors section?
>
>   It sounds like all your predictors are categorical (although we don't
> know about Treatment), so centering isn't really as important/as practical
> an option (you can use sum-to-zero contrasts, but it probably won't
> make a big difference).
>
>   Ben Bolker
>
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