Re: st: Indexing Question

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

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!

Kelly



> From: Ulrich Kohler <kohler@wz-berlin.de>
> Reply-To: statalist@hsphsun2.harvard.edu
> To: statalist@hsphsun2.harvard.edu
> Subject: Re: st: Indexing Question
> Date: Mon, 29 Aug 2005 18:00:20 +0200
>
> . by id (date), sort: gen change = (X[_N]-X[1])/X[1] * 100
>
> Uli
>
> kelly johnson wrote:
> > I have a question regading calculations and indexing. Below I have an
> > except of a larrge data set. How can I calculate the percentage change 
> in
> > the variable X from the earliest date to the last date (e.g. in the case
> > where id==1, the percentage change in X from 7/1/05-7/6/05). I want to 
> do
> > this by id for all my observations (i have thousands of obsevations and 
> the
> > date periods are of varying lengths...). I know it's of the 'by id:' 
> type
> > of statements, but I just can't get it right. Thank you.
> >
> > Kelly
> >
> >
> >         date   id       X
> >      7/1/05    1      .2
> >      7/2/05    1      .3
> >      7/3/05    1      .2
> >      7/4/05    1      .1
> >      7/5/05    1      .5
> >      7/6/05    1      .6
> >     6/16/05    2      .4
> >     6/17/05    2      .4
> >     6/18/05    2      .4
> >     6/19/05    2      .2
> >     6/20/05    2      .1
> >     6/21/05    2      .3
> >     6/22/05    2      .5
> >     4/11/05    3      .2
> >     4/12/05    3      .8
> >     4/13/05    3      .7
> >     4/14/05    3      .8
> >     4/15/05    3      .2
> >     4/16/05    3      .2
> >     4/17/05    3      .3
> >     4/18/05    3      .1
> >     4/16/05    3      .5
> > ...
> >
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