st: check if string or numeric

[Jacob Wegelin <jwegelin@vcu.edu>]

I would like to check for type of variable (string, numeric, etc) in a program, and then take action on the basis of the type. For instance, if it's string, I encode it; else I leave it as is.

The following klugey program seems to solve the problem *part of the time*. But certainly there is a more elegant way?

capture program drop checkIfString
program define checkIfString, rclass
	di "check if `1' is string or numeric"
	quietly tabulate `1'
	local NobsRegardlessOfStringOrNumeric=r(N)
	quietly summarize `1'
	local NobsOnlyIfNumeric=r(N)
	di "NobsRegardlessOfStringOrNumeric: `NobsRegardlessOfStringOrNumeric' and NobsOnlyIfNumeric: `NobsOnlyIfNumeric'"

	if (`NobsRegardlessOfStringOrNumeric'>0) & ( `NobsRegardlessOfStringOrNumeric'  == `NobsOnlyIfNumeric' ) {
			return local type="numeric"
		}

	else {

		if (`NobsRegardlessOfStringOrNumeric'>0) & ( `NobsOnlyIfNumeric'==0 ) {
				return local type="string"
			}

	else {
			return local type="not sure"
			}

	}
end

clear
set obs 5
gen x=_n
gen y="a"
gen z=.
gen w=""

list

checkIfString x
return list
checkIfString y
return list
checkIfString z
return list
checkIfString w
return list


This seems like a FAQ but I haven't found the answer yet on the Web.

Thanks for any tips

Jake

Jacob A. Wegelin
jwegelin@vcu.edu 
Assistant Professor
Department of Biostatistics
Virginia Commonwealth University
730 East Broad Street Room 3006
P. O. Box 980032
Richmond VA 23298-0032
U.S.A. 
http://www.people.vcu.edu/~jwegelin
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