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st: counting observations

From   Jurgen Sidgman <>
Subject   st: counting observations
Date   Wed, 29 Dec 2010 18:32:41 -0600


I have a dataset that has observations for each day of many months. What I need to do is: for each month I need to add all observations for each of the previous 3 months. For example, for january I need to add all observations from October to December from the previous year. Next, for february I need to add all observations from November to January and so on. What I have been doing so far is calculating the cumulative value for each month as follows:

. sort obsdate
. egen count_obs = count(obsdate) if year(obsdate) == 2004 & month(obsdate) <= 3 (this is for the first time I perform the calculation)

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