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st: RE: RE: count non-missing elements in a series


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: RE: count non-missing elements in a series
Date   Thu, 25 Mar 2004 10:32:46 -0000

I switched identifiers partway through this. 

For "id" read "country", throughout. 

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

> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of Nick Cox
> Sent: 25 March 2004 10:24
> To: statalist@hsphsun2.harvard.edu
> Subject: st: RE: count non-missing elements in a series
> 
> 
> You don't give a very clear idea 
> of your data structure. I guess that you 
> have panel data, something like 
> 
> . tsset country year 
> 
> and a series of variables for different 
> industries, say 
> 
> industry1-industry10 
> 
> What you want in question 1 can be got in 
> various ways. Here is one: 
> 
> The first value for each panel is 1 if 
> the investment value is not missing and 0 otherwise: 
> 
> . by id : gen nrun = !mi(industry1) if _n == 1 
> 
> Subsequent values are always 0 if the investment 
> value is missing and 1 greater than the previous 
> otherwise. 
> 
> . by id : replace nrun = 
> 	cond(mi(industry1), 0, nrun[_n-1] + 1)  if _n > 1 
> 
> Another way of doing it is to use -tsspell- from SSC. 
> Install that by 
> 
> . ssc inst tsspell
> 
> Then for say -industry1- the definition of a spell is 
> just a sequence of non-missing values of -industry1-. 
> 
> . tsspell, c(industry1 < .) 
> 
> The variable _seq created by -tsspell- is what 
> you want. Spells automatically are determined 
> separately by panel. 
> 
> If different industries have different patterns
> of missing values, you would need something 
> more like this: 
> 
> forval i = 1/10 { 
> 	tsspell, c(industry`i' < .) spell(_spell`i') 
> seq(_seq`i') end(_end`i') 
> } 
> 
> After which you might want to -drop- some of the created variables. 
> 	
> Nick 
> n.j.cox@durham.ac.uk 
> 
> Oleksandr Shepotylo
> > 
> >     I am using perpetual inventory method to calculate 
> > capital stock but my
> > dataset has a lot of missing data on investment. I have two 
> questions:
> > 
> >     1. For any given country and industry, I want to create 
> > an index that
> > will tell me how many
> > non-missing numbers in a row I have prior to any year t.
> >  For example,  I have investment data for country i and 
> > industry j starting
> > from 1965 to 1975 then missing in 1976-1977 and continuing in 
> > 1978-2001. The
> > index should start from 1 in 1965 till 11 in 1975. then it 
> equals 0 in
> > 1976-1977 and starts from 1 again in 1978.
> > 
> >     2. Less important, but still interesting. How to  impute 
> > missing data if
> > the gap- like in previous example- is less or equal to 2? 
> > Imputation can be
> > based on average growth in capital stock for last 3 years.
> 
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