# RE: st: calculation problem

 From steven proud To Subject RE: st: calculation problem Date Mon, 26 Nov 2007 21:31:07 +0000

```
OK, first of all, you need to set the time (panel) variable
tsset cs ts

Then, you could create
gen lagx=l1.x
gen changex=abs((x-lagx)/lagx)
gen lagchangex=l1.lagchangex
gen lag2changex=l2.lagchangex

gen y=(changex+lagchangex+lag2changex)/3

Yours,
Steven Proud

> Date: Mon, 26 Nov 2007 22:08:39 +0100
> Subject: st: calculation problem
> From: west--@libero.it
> To: statalist@hsphsun2.harvard.edu
>
> Dear friends, I need a little help to solve a calculation.
> I have a panel database (cs and ts), and for one variable, say "x", I need to calculate the following formula:
>
> y = summation_(i= t-2 to t) of (1/3)* abs[( x_i - x_i-1 )/ x_i-1 ]
>
> In other words, "y" is the three-year average variation in % of "x". I would get a new column for each firm-year data. Could anybody help me? Thanks in advance!
>
> D.
>
>
> *
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> * http://www.ats.ucla.edu/stat/stata/

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