Dear List:
 
I have a data set with over 7000 students with about 4 observations over time per student. I want to examine the within-group fits of a random sample of this group as it takes forever to compute and draw all 7000 regressions.
 
Here is the code I have used so far. 
 
>group<-groupedData(math~year|childid, data=scores)
>group.list<-lmList(group)
>plot(augPred(group.list))
 
How might I select a random sample of say 100 students so that I can visually examine their trajectories?
 
Thank you
 
------
Harold C. Doran
Director of Research and Evaluation
New American Schools
675 N. Washington Street, Suite 220
Alexandria, Virginia 22314
703.647.1628
 <http://www.edperform.net/>  
 
 
 

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