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Re: st: My last word on strange world
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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