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AW: st: on data transformation

Subject   AW: st: on data transformation
Date   Wed, 20 Jul 2011 21:21:51 +0100 (BST)

Dear Nick,

thanks a lot! This was very helpful. Indeed, the event variable takes the value 
of 1 at the time of event and zero before that. 

I have just a quick question: how shall I proceed if I need to keep the year 
when the event has occurred and the previous year but drop any other preceding 


----- Ursprüngliche Mail ----
Von: Nick Cox <>
Gesendet: Mittwoch, den 20. Juli 2011, 21:49:22 Uhr
Betreff: Re: st: on data transformation

It is not clear what value -event- takes when it is not 1. I will suppose 0.

bysort x year (event) : gen occurred = event[_N]

spreads occurrences to all the weeks in the year in which they occurred.

keep if occurred

then -drops- entire years without events.


On Wed, Jul 20, 2011 at 2:41 PM,  <> wrote:
> I would like to ask for help with data transformation. I have data on objects
> x1, x2,x3  that are observed over time (weeks). I have variables var1 and var2
> for each objects and also variable indicating the year of observation. In
> addition, a variable "event" indicates the time period when an event has
> occurred.
> The columns of the panel data set look as follows:
> x  week      var1  var2 year event
> x1 2006w2 var1 var2 2006
> x1 2006w3 var1 var2 2006
> x1 2006w4 var1 var2 2006
> x1 2007w7 var1 var2 2007
> x1 2007w8 var1 var2 2007
> x1 2007w9 var1 var2 2007
> x1 2007w10 var1 var2 2007 1
> x2 2008w2 var1 var2 2008
> x2 2008w3 var1 var2 2008
> x2 2008w4 var1 var2 2008
> x2 2009w9 var1 var2 2009
> x2 2009w8 var1 var2 2009
> x2 2009w9 var1 var2 2009
> x2 2009w10 var1 var2 2009 1
> I have many variables x that differ in number of weeks and years. I need 
> to keep the year when the event has happened and dropped any previous years.
> Given my data set, is this possible to be done in Stata?

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