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prolog
2011 Mar 21
3
Computing row differences in new columns
...e. I'd like to compute the differences in dates and results for each patient, based on the previous row. Obviously the last entry for each subject should be a NA.
Which would be the best way to accomplished that ?
I guess questions like that have been already answered a thousand times, so I apologize for asking one more time.
Thanks
Roberto
SUBJECT
Date
Result
DateDiff
ResultDiff
10751
22-Jul-03
3.5
10751
13-Feb-04
1.3
10751
20-Aug-04
1.6
10751
08-Mar-05
1.7
10751
30-Aug-05
1.6
10751
21-Feb-06
1.3
10751
31-Aug-06
1.2
10751
27-Feb-07
1.5
10751
29-Aug-07...