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Re: st: missing values


From   Richard Williams <Richard.A.Williams.5@ND.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: missing values
Date   Thu, 22 Sep 2005 06:11:50 -0500

At 01:11 AM 9/22/2005, you wrote:
Here are my exact commands.

replace sswlnw_1 = .a if (yob > 1912 & a_age > 69)
replace sswlol_1 = .a if (yob > 1912 & a_age > 69)
replace sswlnw_2 = .a if (yob > 1912 & a_age > 69)
replace sswlol_2 = .a if (yob > 1912 & a_age > 69)

If I use . instead of .a, 0 changes are made. (With .a, 57981 changes re made)

If I say gen dummy = 0
replace dummy = 1 if (yob > 1912 & a_age > 69)
then 57891 changes are made...
Incidentally, here is a pseudo-cloning of what you are doing (I think):

. sysuse auto, clear
(1978 Automobile Data)

. gen dummy = 0

. replace dummy = 1 if (mpg > 20 & trunk > 15)
(6 real changes made)

. replace price = . if (mpg > 20 & trunk > 15)
(6 real changes made, 6 to missing)

. sysuse auto, clear
(1978 Automobile Data)

. replace price = .a if (mpg > 20 & trunk > 15)
(6 real changes made, 6 to missing)

As you see, it seems to work fine, regardless of whether I use . or .a.

One other Q: What version of Stata are you using? Is it up to date? I remember there was some problem with Stata a while back where it was behaving in odd ways with MD, but then an update fixed it. I don't know if that might apply here or not.


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Richard Williams, Notre Dame Dept of Sociology
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