Ask for Help with Computation of Running Sum of a Variable within Multiple Variables in Stata.

[smith Jason]

The long format dataset is presented as follows.
It has 3 columns,
gender (male=1; female=2),
period (1=elementary school;2=middle school;3=high school);
pat=average physical activtiy time per day.
Now, I want to use Stata code to create a new column daily_pat,
which should be equal to the running sum of pat by gender and period.
Thank you for your help!

* Example generated by -dataex-.
clear
input byte (gender period pat)
1 1 11
1 1 11
1 1 11
1 2 15
1 2 15
1 2 15
2 1 11
2 1 11
2 1 11
2 2 12
2 2 12
2 2 12
end

[Leonardo Guizzetti]

Hi Jason, I answered this in your previous thread.

[smith Jason]

Thank you!