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RE: st: My last word on strange world

From   Richard Williams <[email protected]>
To   [email protected], <[email protected]>
Subject   RE: st: My last word on strange world
Date   Thu, 10 Jan 2008 11:18:28 -0500

At 10:36 AM 1/10/2008, Nick Cox wrote:
On (a), list members can test themselves. Suppose x is missing on some
observations. What do you consider appropriate Stata behaviour for

. list x if x > 42
Do not list the case if x is missing. Let us say x is age. If I give a command like this, I probably want those older than 42, not people whose age is missing.

. regress z y if x > 42
Do not include the case if x is missing. If i do this, I want to restrict my sample by age, and I probably don't want to include those whose age is unknown.

If by some chance I do want the missings included, I can always change the ifs to

if x > 42 | missing(x)

I think I am much more likely to want the missings excluded rather than included, hence I would make you go to the extra work when you want them included, rather than make you work harder when you want them excluded.

Intuitively, most people don't think of missing as being a really really large number. For that matter, missing could just as easily have been coded as a really really small number. To most people, missing is just missing, and the fact that missing has to be assigned a number is just a necessary evil. I assume SPSS assigns system missing a number too, but I have no idea whether it is a big number or a small number, nor does their seem to be much reason I would need to know (because missing is one of the very few areas where SPSS is more logical than Stata!)

That is how I would have Stata behave if I was designing it from scratch. Changing its behavior after it has done something a particular way for 20 years may be another matter.

Richard Williams, Notre Dame Dept of Sociology
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