Rationale behind egen's anymatch() with -if-

[Andrea Discacciati]

I wonder what's the rationale behind the behaviour of egen's anymatch() and anycount() functions when used together with an -if- statement.

From the help file:

Values for any observations excluded by either if or in are set to 0 (not missing).

This seems like a major deviation from Stata's standard way of generating new variables in the presence of an -if- statement. I'm not complaining, as this exception is clearly reported in the help file. I'm just curious.

[Nick Cox]

An advantage of this choice is that statements with the skeleton form

egen wanted = anymatch() 

can be followed by

... if wanted

as an easy idiom.

[Andrea Discacciati]

Thank you, Nick.