Stata 11 help for sign help sign() ------------------------------------------------------------------------------- Title [D] functions -- Functions Mathematical function sign(x) Domain: -8e+307 to 8e+307 and missing Range: -1, 0, 1 and missing Description: returns the sign of x: -1 if x < 0, 0 if x = 0, 1 if x > 0, and missing if x is missing. Also see Manual: [D] functions Help: [D] functions, [D] functions (math functions)