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st: RE: re: cond(a,b,c) fn


From   "Scott Merryman" <smerryman@kc.rr.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: re: cond(a,b,c) fn
Date   Thu, 14 Apr 2005 21:48:42 -0500

A couple other ways:

gen a = cond(rep78==1, 1, 0 ) if rep !=.


gen a = cond(rep, cond(rep ==1, 1, 0), 0, .)

Scott

> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-
> statalist@hsphsun2.harvard.edu] On Behalf Of Kit Baum
> Sent: Thursday, April 14, 2005 9:43 PM
> To: statalist@hsphsun2.harvard.edu
> Subject: st: re: cond(a,b,c) fn
> 
> James writes
> 
> When I use the cond(x,a,b,c) function, I could not generate the value c
> when x is missing. For example:
> 
> sysuse auto, clear
> tab rep78, mi
> gen a=cond(rep78==1, 1, 0, .)
> tab a, mi
> 
> It gives
> 
> a	Freq.	Percent	Cum.
> 
> 0	72	97.30	97.30
> 1	2	2.70	100.00
> 
> Total	74	100.00
> 
> There should be 5 missing values for variable a according to the manual.
> Thanks for your input.
> 
> 
> 
> The online help says
> 
>   cond(x,a,b,c) returns a if x evaluates to true (not 0), b if x
> evaluates to false
>          (0), and c if x evaluates to missing (.).
> 
> Since "rep78==1" never evaluates to missing, a will never be set to
> missing.
> A way to achieve this is
> 
> . g a = (rep78==1)*rep78/rep78
> 
> . tab a,mi
> 
>            a |      Freq.     Percent        Cum.
> ------------+-----------------------------------
>            0 |         67       90.54       90.54
>            1 |          2        2.70       93.24
>            . |          5        6.76      100.00
> ------------+-----------------------------------
>        Total |         74      100.00
> 
> Kit Baum, Boston College Economics
> http://ideas.repec.org/e/pba1.html
> 
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