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st: Adding up prior iterations of a variable in a time series dataset


From   Benedikt Achatz <benedikt.achatz@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: Adding up prior iterations of a variable in a time series dataset
Date   Sun, 24 Jun 2012 16:41:47 +0200

Hello,

I am a student and rather new to Stata, and i just can't figure out how this works. I have been browsing the web for some time and haven't found a solution that worked for me.

I have a dataset that contains observations of websites at different points in time. There is a variable, clicks, that contains the clicks in one time period. What I need to do now is to create a variable clicks_to_date that contains the clicks in every time period before the current one, including that one.

This is the code I have been using thus far, without much success...

   levelsof page_id, local(pg_id)
   levelsof time_var, local(tm_vr)

   cap drop clicks_to_date
   gen clicks_to_date = 0

   local clicks_old = 0
   foreach id in `pg_id'{
        foreach x in `tm_vr'{
        if `x' == 1 {local clicks_old = 0
        }
        replace clicks_to_date = clicks+`clicks_old'
        display `clicks_old'
        local clicks_old = clicks_to_date
        }
   }

Can anyone please hint me into a direction how this could be done?

Thanks,

Ben
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