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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   Fri, 11 Jan 2008 12:08:34 -0500

At 11:35 AM 1/11/2008, William Gould, StataCorp LP wrote:
It therefore follows

     x>=100      evaluates to false if x is missing

and thus the statements (x>=100) and (x<100) are both false and, as I asked
about Jeph's comment, is that really in line with the expectations of
ordinary users?
It is with mine. To me, missing is not a number, large or small. And, because of that, in practice the coding is usually more like

x > = 100 & !missing(x)

which I find awkward and mistake prone. My own preference would therefore be that the statements be more like

x>=100
x<100
missing(x)

One and only one of the above three would be true. This also makes it explicit that how to handle missing is a separate decision.

There are going to be gotchas with any system. I therefore think that the default should be whatever people are likely to want most frequently. And I think it is relatively rare that when you have a statement like

x>=100

that people intend for missing to be evaluated as true. If they do, that is when they can go to the extra work and code

x>=100 | missing(x)


-------------------------------------------
Richard Williams, Notre Dame Dept of Sociology
OFFICE: (574)631-6668, (574)631-6463
HOME: (574)289-5227
EMAIL: [email protected]
WWW: http://www.nd.edu/~rwilliam

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