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Date:         Tue, 5 Jan 2010 10:50:25 -0500
Reply-To:     Peter Flom <peterflomconsulting@mindspring.com>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Peter Flom <peterflomconsulting@MINDSPRING.COM>
Subject:      Re: New Comparison Operators? - WAS: missing numerical values = -
Comments: To: Lou <lpogoda@HOTMAIL.COM>
Content-Type: text/plain; charset=UTF-8

>"Jonathan Goldberg" wrote >> This is a hoary question. Logically speaking, having x < 2500 resolve to >> true when x is missing is absurd, and having x = y resolve to true when >> both x and y are missing is ludicrous. Missing means "I don't know." If >> x and y are heights, you are claiming that you know that two heights are >> equal when you don't know what either of them is. >

Lou replied

>At the risk of seeming the fool, I've always thought of it as: > >if X = "I don't know" and y = "I don't know" then x does equal y.

Hmmm... paraphrasing Bill Clinton

"It depends on what your definition of equals equals". :-)

In the example Jonathan used, a person might not know their height, but probably knows it approximately.

A person who thinks she is about 5'1", but says "I don't know" because she isn't sure, maybe she's 5'0", does NOT equal a man who thinks he's 6'2", but might be 6'1".

Of course, that's a little silly, but it's easy to come up with much less silly examples.

On this, I like the R method better. If you ask if missing = missing, you get missing.

Peter

Peter L. Flom, PhD Statistical Consultant Website: http://www DOT statisticalanalysisconsulting DOT com/ Writing; http://www.associatedcontent.com/user/582880/peter_flom.html Twitter: @peterflom


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