Question

I am writing a Stata do file and I would like to provide default values if the user does not supply some parameters. To do so, I woud like to check if a macro is undefined.

I have come up with a hacky way to do this:

*** For a local macro with the name value:
if `value'1 != 1 {
    ...do stuff
}

But I would like to know if there is a idiomatic way to do this.

Answer 1

If it’s undefined, the contents of the macro would be empty. You can do this:

if missing(`"`mymacroname'"') {
    display "Macro is undefined"
}

The quotes aren’t really needed if the macro will contain a number. The missing(x) function can handle strings and numbers. It is kind of like testing (x=="" | x==.) Placing `' around "`mymacroname'" allows the macro to contain quotes, as in local mymacroname `"foo"' `"bar"'.