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st: RE: counting observations

From   "Keith Dear" <>
To   <>
Subject   st: RE: counting observations
Date   Thu, 30 Dec 2010 15:55:59 +1100

You say you want to "add" the observations, but apparently you do mean
to count them, not sum them...
Does this do it?

	gen int ym=mofd(obsdate)
	collapse (count)n=obsdate, by(ym)
	format n %6.0g
	tsset ym

	* next two lines unnecessary if every month was present
	replace n=0 if n==.

	gen long c3 = l1.n + l2.n + l3.n	// see -help tsvarlist-

If desired, you could then merge this back onto the original dataset.

-----Original Message-----
[] On Behalf Of Jurgen
Sent: Thursday, 30 December 2010 11:33 AM
Subject: st: counting observations


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

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