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: [email protected]
> To: [email protected]
>
> 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.
>
>
> *
> * For searches and help try:
> * http://www.stata.com/support/faqs/res/findit.html
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
_________________________________________________________________
Celeb spotting – Play CelebMashup and win cool prizes
https://www.celebmashup.com
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
