st: Using the -if- qualifier with a string variable

["louis boakye-yiadom" <louisby@hotmail.com>]

Dear All,
Can the -if- qualifier be used with a string variable? If so, how is it 
done? I gave the following command, and had the shown result:
. keep if facility==bir
bir not found
r(111);

"facility" is a string variable and "bir" is one of the values "facility" 
takes. Thank you.

Louis


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