[R-sig-ME] How to extract num. of observations and groups used in a mixed model using gee package

[David Winsemius]

On Apr 24, 2012, at 12:43 AM, david oseguera montiel wrote:

> I meant the grouping

> factor in the model indicated by id. From gee documentation 'id = a  
> vector which identifies the clusters..'. So in the warpbreaks data  
> set, id = wool has 54 obs, in two clusters (groups).
> library(gee)
> library(Hmisc)
> > describe(warpbreaks$wool)
> warpbreaks$wool
>      n missing  unique
>     54       0       2
>
> A (27, 50%), B (27, 50%)

So you would use this information to direct your search:

summgee <- summary(gee(breaks ~ tension, id=wool, data=warpbreaks,
                     corstr="exchangeable"))

summgee$call$id
# wool
length(levels(warpbreaks[[as.character(summgee$call$id)]]))
#[1] 2

>
>
>
> On 23/04/2012 22:57, David Winsemius wrote:
>>
>> On Apr 23, 2012, at 11:25 PM, david oseguera montiel wrote:
>>
>>> David,
>>> Thank you very much. Number of observations solved, but I am still  
>>> missing how to find out the number of groups used. In the  
>>> warpbreaks data set these are 2. Any ideas. Thank you.
>>>
>> I must be unclear what you mean by "number of groups".
>

David Winsemius, MD
West Hartford, CT