
Dear friends,
I have struggled to do what is likely rather simple but cannot get it working.
I have a dataframe with 428 obs. of 5 variables on 26 patients. Two 
variables are responses, one an index of patients (1:26), one a 
period-indicator :1 :max 3, and one total time from min 1 to max 36 weeks 
(max 21 entries). A complete set would be 26*21=546 long but here are only 
428 entries.
Now, within each period nested within patients a max of one of the response 
variables is found, with length 78, 6 are NA from MAX <- 
by(response,list(period,id),max).
Then how do I get the individual times corresponding to these within 
period, within patient MAX values ?
(Windows R 1.7)

Best wishes
Troels


Troels Ring, MD
Department of Nephrology
Aalborg Hospital, Denmark
tring@gvdnet.dk
fax 00 45 99 32 22 34
tlf 00 45 99 32 22 42
  00 45 98 14 05 82 (home)
Heliosvej 12
9210 Aalborg SE
Denmark 
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