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plm random effect: the estimated variance of the individual effect is negative

3 messages · matteo ognibene, David Winsemius

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On Jan 3, 2013, at 8:19 AM, matteo ognibene wrote:

            
Head up; matteo: This is pretty much unreadable (due to the failure to  
follow the recommended posting procedure.)
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You're right David, I'm really sorry. I deactivated html, hope now it works.
I have a problem with the variance estimation in a random effect model


I used this formula to get my result, and it works:
but when i split my dataframe into several groups it gives me this error:
The code i used to split the dataframe is:
I want to point the all the code works perfectly in a within model, and I tried using all the random.method for the variance estimation.
In addition I used the same random effect model in Stata and it works... (and for the within model the results are identical in R and Stata)


I'll be really gratefull if someone can help me.


Thanks,
Matteo