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From |
Nick Cox <njcoxstata@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Counting using a rolling time window |

Date |
Tue, 10 May 2011 14:48:49 +0100 |

I imagine your example is to be taken with the correction that the first 1997m8 should be 1997m7. I suggest bysort id (time) : gen count = sum(action) - sum(action[_n-3]) See also comments in <http://www.hsph.harvard.edu/cgi-bin/lwgate/STATALIST/archives/statalist.1105/date/article-397.html> on the expression "a code", which I warn against. Nick On Tue, May 10, 2011 at 2:12 PM, Louis, Philippe <Philippe.Louis@econ.kuleuven.be> > I have the following problem. My dataset contains an id-number, a time variable measured in months, and a binary variable indicating action or no action. The time frame is not the same for each person (i.e. id 1 is monitored between January 2000 and May 2000, id 2 between August 1997 and October 1997, etc.). The action variable records whether an action happened during that month or not. > > I would like to create a new variable that counts the number of positive actions (i.e. action variable equal to 1). More specifically, I am looking for a code that would loop through the dataset and that would count the number of action==1 using a three months' time window (i.e. current month + 2 previous months), resetting the counter at every new id. If less than three months are available, the loop should just count the number of action==1 of the available months. > > An example: > Id time action count > 1 2000m1 1 1 > 1 2000m2 1 2 > 1 2000m3 1 3 > 1 2000m4 0 2 > 1 2000m5 0 1 > 2 1997m8 0 0 > 2 1997m8 1 1 > 2 1997m9 0 1 > 2 1997m10 1 2 > > I have been struggling for a while to write a code that would generate the count variable. > > Any help or suggestions would be appreciated. * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**RE: st: Counting using a rolling time window***From:*"Louis, Philippe" <Philippe.Louis@econ.kuleuven.be>

**References**:**st: Counting using a rolling time window***From:*"Louis, Philippe" <Philippe.Louis@econ.kuleuven.be>

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