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st: Re: RE: Re: MIME-Version: 1.0


From   "Sergiy Radyakin" <Radyakin@aoek.uni-hannover.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Re: RE: Re: MIME-Version: 1.0
Date   Tue, 20 Feb 2007 15:45:10 +0100

Hi Maarten,

I do not agree. I assume that the variable was split in such a way that the data from it was redistributed over a number of empty (all having default . values) variables.

But what is more important, is whether the initial variable ITSELF HAD MISSING values!? If so, those must also be recreated. Say there was a value ".a" initially, now var1==.a, var2==.

var3==. (by construction)

your code will leave var3==.
Although one would like to see ".a" there!

My code will keep the LAST non "." value which can be ".a" and it only yields "." if all the vars (1 and 2 in the example) have ".". It will correctly recreate the initial variable if it was splitted over the area of empty variables (all cells ==. ). Yours will not recreate any .a, .b, ...

Generally, say if the initial variable was spread over a matrix of values v, one must write:
gen var3=`v'
replace var3=var1 if var1!=`v'
replace var3=var2 if var2!=`v'

Where `v' is a local variable. I just set v=. since this is the default value.

Whether it has a practical significance, I don't know (not enough info from the author of the question).
Was there any attachement to this message?

Regards, Sergiy

----- Original Message ----- From: "Maarten Buis" <M.Buis@fsw.vu.nl>
To: <statalist@hsphsun2.harvard.edu>
Sent: Tuesday, February 20, 2007 3:18 PM
Subject: st: RE: Re: MIME-Version: 1.0



--- Sergiy Radyakin wrote:
 var1    var2
1        .
2        .
>3        .
.        1
>.        2
.        3

gen var3=.
replace var3=var1 if var1!=.
replace var3=var2 if var2!=.
Good idea, and it work in your example, however Stata knows
multiple types of missing data (. .a .b .c ...), see
-help missing-. So it might be safer to use:
replace var3=var1 if var1<.
replace var3=var2 if var2<.

Hope this helps,
Maarten

-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------



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