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st: RE: RE: RE: copy values


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: RE: RE: copy values
Date   Thu, 11 Dec 2008 19:59:54 -0000

That's good to hear, but such code risks copying across states, which I
guess you do not want. 

Adding 

... if state == state[_n-1] 

is one way to ensure that, given sensible sort order. Doing things -by
state- is an even better way. 

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

Victor, Jennifer Nicoll

Thanks.  The following command worked perfectly.  Sorry I didn't look
for it in the FAQs.

replace blackstate = blackstate[_n-1] if blackstate >= .

Nick Cox

This is an FAQ. 

FAQ     . . . . . . . . . . . . . . . . . . . . . . . Replacing missing
values
        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N.
J. Cox
        2/03    How can I replace missing values with previous or
                following nonmissing values?
                http://www.stata.com/support/faqs/data/missing.html

-- apart from the twist about -drop-ping values which is standard stuff.

Victor, Jennifer Nicoll

I have a time series panel that has missing values.  I want to copy,
duplicate, replace, or otherwise fill-in values in one variable with
other values in that variable.

For example, suppose I have variables time, state, district,
blackpopdist (black population in that district) and blackpopstate
(black population in that state.  My unit of analysis is district, so
states are listed as district=0.  I have blackpopdist for each
district>0, but missing for district==0.  I have blackpopstate for each
district==0, but missing otherwise.  I want to ultimately delete the
observations where district =0. Before I do so, I want my blackpopstate
variable to take on constant values for that state, for how ever many
districts are in it.  Therefore, for each year-state, I want to
duplicate the first value in blackpopstate to fillin the other missing
value for the rest of the districts in that year-state.  Then drop the
district=0 observation.

A sample starting dataset:
Time	state	dist	blackpopdist	blackpopstate
92	AL	0	.		1234
92	AL	1	234		.
92	AL	2	456		.
92	CA	0	.		4567
92	CA	1	2345		.
92	CA	2	12		.
93	AL	0	.		1235
93	AL 	1	235		.

A sample complete dataset:
Time	state	dist	blackpopdist	blackpopstate
92	AL	1	234		1234
92	AL	2	456		1234
92	CA	1	2345		4567
92	CA	2	12		4567
93	AL 	1	235		1235


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