[R-sig-ME] repeated measures: levels of grouping factor must be less than number of obs

[Andrew Miles]

Just to clarify, when you say repeated measures do you mean that you  
have data from multiple individuals from the same family?  Or do you  
mean that you have data on the same individuals across multiple time  
points (ex. data from person one on Monday, and Tuesday, and  
Wednesday, etc.)?  The latter is what is more traditionally referred  
to as a repeated measures study; the first is simply clustering in the  
data.

If the first (i.e. the clustered data), the model you have specified  
is sufficient.  Specifically, it will estimate a variance component  
that will tell you how much variation there is in y between family  
groups.

Hope that helps.

Andrew Miles


On Apr 18, 2011, at 11:33 AM, Brent Pedersen wrote:

> hi, I posted this to the main R mailing list a while back and people
> directed me to
> the lme4 package and this mailing list so I thought I might get more
> help here...
>
> We have some data, a subset of which is pasted at the end of this  
> message.
> I am trying to understand how to do repeated measures as our study
> design consists of a subject (proband) and 1 or 2 siblings.
>
> Thus far, our model looks like this--with family_id indicating a
> sibling relationship:
>
>> model = lmer(y ~ concordant + age.proband + age.other + sex.proband  
>> + sex.proband + sex.other + (1| family_id), data=df2)
>
> is the above formulation sufficient to capture the repeated measures  
> by family?
> Next, when I do this with lme4a, I get an error:
>
>  Error in lmer(y ~ concordant + age.proband + age.other +  
> sex.proband +  :
>    number of levels of each grouping factor must be less than number  
> of obs
>
> I have seen this thread:
> http://permalink.gmane.org/gmane.comp.lang.r.lme4.devel/3313
> but the change does not appear to be included in the latest lme4a
> package from Rforge, is there another repo where this has been
> incorporated? or is this an error on my part?
>
>
> thanks,
> -brent
>
> concordant  family_id   external_ref.proband    external_ref.other
> sex.proband sex.other   age.proband age.other   y(fake)
> T   58  80015550    80015543    M   F   15  19  1
> F   58  80015550    80016946    M   F   15  8   2
> T   54  80015499    80015338    F   F   5   7   3
> F   54  80015499    80013112    F   M   5   13  4
> F   22  80012269    80012252    F   F   12  10  5
> F   22  80012269    80018691    F   M   12  8   5
>
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