[R-sig-ME] repeated measures: levels of grouping factor must be less than number of obs
Andrew Miles
rstuff.miles at gmail.com
Mon Apr 18 17:44:36 CEST 2011
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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