st: Averages between dates that are different for each agent

["Miguel A. Duran" <maduran@uma.es>]

Hi, Statalisters. Maybe someone could help me to solve the following
problem. In a panel dataset, I would like to calculate the average value of
a variable for each agent, but the number of periods to be considered is
different for each agent. The following example might help to understand
what I mean (and to show how my dataset is, in a simplified version,
structured):

Agent   Period      Var    Startdate   Enddate
  1              t1          11           t2               t3
  1              t2          12           t2               t3
  1              t3          13           t2               t3
  1              t4          14           t2               t3
  2              t1          21           t1               t4
  2              t2          22           t1               t4
  2              t3          23           t1               t4
  2              t4          24           t1               t4

According to what startdate and endate indicate, I would like to calculate
the average of var for agent 1 between t2 and t3, whereas for agent 2 the
period to calculate the average of var goes from t1 to t4.

Thanks in advance for your help.

Miguel.

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