st: bysort, forvalues and _N

[Constantin Alba <constantin.alba@gmail.com>]

Dear statlist members,

I am trying to find a solution for the following problem.

I have a dataset organized by personID, for each personID there are
startDate and Duration for various activities.

I want to find out how many activities a person performs at the same
time (e.g. something like workload)

logically i see it like this:

sort personID startDate Duration

by personID: forvalues i=1/`=_N' {
                                   "compare current date with all
other prior dates+duration
                                       and update counter accordingly"
                                      }

however, by and forvalues do not work together, so i am trying to find
an alternative way to do so.


thank  you in advance

C.
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