```Date: Tue, 5 Jan 2010 10:50:25 -0500 Reply-To: Peter Flom Sender: "SAS(r) Discussion" From: Peter Flom Subject: Re: New Comparison Operators? - WAS: missing numerical values = - Comments: To: Lou 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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