st: comparing contents of two columns (variables)

[James Bernard <jamesstatalist@gmail.com>]

Hi all,

I was wondering if you know of any command in stata that can compare
contents of two columns. Imagive I have two columns

  A                 B
-------           ---------

304             112
203             123
776             304
334             555
212             111
111             444
123             999
200
300
277

Now I want to count how many of the contents of column B cannot be
found in column A (which is 5 out of 7)

I looked up the web and found that someone talked about a command
called CF3, but I could not get anything more about this command.

Thanks in advance

James
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