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st: the -missing- command


From   "louis boakye-yiadom" <louisby@hotmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: the -missing- command
Date   Mon, 10 Oct 2005 15:06:59 +0000

Dear All,
I have two questions regarding the -missing- command (or function?).
First question:
I'm not clear about exactly what -missing- does. An example will clarify my concern. I have a dataset containing 11 variables (the first is -clust- and the last is -s11aq13-). One of the variables is -trexpcd-, and the total number of observations is 4872. I gave the following commands and had the shown output:
count if mi(trexpcd)
4649
count if mi(clust-s11aq13)
82

My understanding of the online -help- is that -missing- evaluates the number of observations for which any of the arguments is missing. So, for the second command, since -trexpcd- is one of the arguments, I expected the result to be a number which is at least equal to 4649.

Can anyone please show me what I'm missing?

Second question:
Also, I had the following result:
count if !mi(clust-s11aq13)
4790

Does !mi() evaluate the number of observations for which none of the arguments is missing? Thank you.

Louis


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