RE: st: Indexing Question

["kelly johnson" <econometrics@hotmail.com>]

What if some observations are only in part of that range? suppose i want to 
calculate the % change in X for all observations from 7/2/05-7/5/05. Since I 
have a large database, there may be observations that are in part of the 
period (e.g. 7/3/05-7/4/05). I want to calculate the % change in X for all 
observations that appear throughout that period, or a portion of that 
period. Also, how can I make it output a single number (for this variable) 
for each id?

Thank you for your assistance.

kelly


> From: "Nick Cox" <n.j.cox@durham.ac.uk>
> Reply-To: statalist@hsphsun2.harvard.edu
> To: <statalist@hsphsun2.harvard.edu>
> Subject: RE: st: Indexing Question
> Date: Mon, 29 Aug 2005 17:26:44 +0100
>
> Your dates are to me ambiguous.
> I'll guess your dates are month/day/year.
>
> gen OK = !inlist(date, d(2jul2005), d(7jul2005))
> bysort id (OK date) : gen pc_change = 100 * (X[2] - X[1])/X[1] if OK[1] == 
> 0 & OK[2] == 0
>
> The trickery with !inlist() is just a way to make the
> sort order convenient. The OK dates will be coded 0
> and sorted to the first two observations in each panel.
>
> The result will be repeated for each observation in the panel.
> Use -egen, tag()- or some other method to select just one.
>
> Note that your example shows repeated values for
> panel 3.
>
> Nick
> n.j.cox@durham.ac.uk
>
> kelly johnson
>
> > What if I want to do the same calculation, but in a specific
> > time period.
> > Eg. in my data set, I want to calculate teh percentage change
> > in X between
> > 7/2/05-7/5/05 (for all observations with data in that time
> > period). Thank you!
>
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