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st: RE: RE: RE: Fixed value - time series


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: RE: RE: Fixed value - time series
Date   Fri, 5 Jul 2002 13:36:56 +0100

Graeme Inglis

> x is a categorical variable and can take the values 1,2,3,4.
> x is taken at periods 0(baseline),1 ,2 ,3,.. and varies over time.
> Values of x at these periods is x0, x1, x2, x3,....
> I want to generate a newvar y = x0, value at baseline, such that
> y0=y1=y2=y3=...
> 
> If I do 'gen y = x if period==0' I only get values for y in period '0'.
> 

If -x- is observed just once when -period- is 0, then 

su x if period == 0, meanonly 

will report on a single observation, and what is 
left behind in r(min), r(max), etc. will be the 
same value, so following with 

gen y = r(min) 

will put the same constant in each value of the variable. 

Alternatively, if 

sort period 

-sort-s the observation with -period- 0 
to the first observation, then following with 

gen y = x[1] 

should suffice. Having said all that, there is 
some inefficiency in holding the same number 
repeatedly. It might be better to hold it in a macro 
or scalar. 

Nick 
n.j.cox@durham.ac.uk 
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