Stata tip: "Mega If" : a simple command to generate long if conditions

Suppose you need to type the following command that has many conditions in the if condition:

replace group = 1 if (benefitNumber == 1 | benefitNumber == 2 | benefitNumber == 3 | benefitNumber == 4 | benefitNumber == 5 | benefitNumber == 6 | benefitNumber == 11 | benefitNumber == 12 | benefitNumber == 17 | benefitNumber == 19 | benefitNumber == 21 | benefitNumber == 22 | benefitNumber == 23)

It's a bit much to type. The program megaif below will generate this long line from the much shorter command:

megaif 1 2 3 4 5 6 11 12 17 19 21 22 23, v(benefitNumber) c(replace group = 1)

The above has lots of "or equals", but you can also generate lots of "and does not equal", for example:

replace group = 1 if (benefitNumber != 1 & benefitNumber != 2 & benefitNumber != 3 & benefitNumber != 4 & benefitNumber != 5 & benefitNumber != 6 & benefitNumber != 11 & benefitNumber != 12 & benefitNumber != 17 & benefitNumber != 19 & benefitNumber != 21 & benefitNumber != 22 & benefitNumber != 23)

using the following command:

megaif 1 2 3 4 5 6 11 12 17 19 21 22 23, v(benefitNumber) c(replace group = 1) e(!=) s(&)

It works for numeric variables and for string variables too. Check this out:

megaif "a b" b "cc" d `"e"', v(benefit_stringvar) c(replace group = 1) e(!=) s(&)

executes the following command:

cmd to execute: replace group = 1 if (benefit_stringvar != "a b" & benefit_stringvar != "b" & benefit_stringvar != "cc" & benefit_stringvar != "d" & benefit_stringvar != "e")

As you can see, for string variables the quotes are optional unless you're checking for text that has a space in it. The program is below. Enjoy!

program define megaif

    // By Shafique Jamal
    // e.g.
    // sysuse auto, clear
    // megaif 0 1, v(foreign) c(drop) e(~=) // this will drop all the observations. Just for illustrative purposes to show how the command could be used
    // another e.g.
    // The command:
    //    megaif 14 15 16 17 18 19 20 21 22, c(gen priv1 = 1) var(income_type2)
    // would execute the following command:
    //     gen priv1 = 1 if (income_type2 == "14" | income_type2 == "15" | income_type2 == "16" | income_type2 == "17" | income_type2 == "18" | income_type2 == "19" | income_type2 == "20" | income_type2 == "21" | income_type2 == "22")


    syntax anything(id="variable and values" name=arguments), Var(varname) Cmd(string) [Equality(string) Separator(string)]
   
    // The default is equality
    if ("`equality'" == "") {
        local equality "=="
    }
   
    if ("`separator'" == "") {
        local separator " | "
    }
    else {
        local separator " `separator' "
    }
   
    cap confirm numeric variable `var'
    if (_rc == 0) { // variable is numeric
        local numericvar = 1
    }
    else {
        local numericvar = 0
    }
    // di "numericvar = `numericvar'"
   
    local count = 0
    local orcondition ""
    foreach w of local arguments {
        local count = `count' + 1

        // di `"w = `w'"'
        if (`numericvar' == 0) {
            local orcondition `"`orcondition'`orseparator'`var' `equality' "`w'""'
        }
        else {
            local orcondition `"`orcondition'`orseparator'`var' `equality' `w'"'
        }
        local orseparator "`separator'"
    }
   
    // di `"orcondition = `orcondition'"'
    di `"cmd to execute: `cmd' if (`orcondition') "'
    // set trace on
    // set traced 1
    `cmd' if (`orcondition')
    set trace off

end