st: generate sum by categorical variable

[Shehzad Ali <sia500@york.ac.uk>]

Hi,

I have an individual patient level data with two variables of interest, one 
is the number of weeks spent by each patient in the study (values between 1 
and 52) and other being stratum they belong to (values between 1 and 3). I 
want to generate a new variable (total_weeks) that summarises the total 
number of weeks spent by each stratum. So the new variable will have 3 
values only, one for each stratum. I can obviously use -sum- and -r(sum) to 
generate separate variables by strata but I was wondering there must be a 
quicker way of doing it in one line. Can you advise please?

Thank you,

Shehzad
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