sysuse nlsw88, clear

gen marst = cond(never_married, 1,              ///
            cond(married, 2, 3))                ///
            if !missing(married, never_married)
label define marst 1 "never married"            ///
                   2 "married"                  ///
                   3 "divorced/widowed"
label value marst marst

gen black = race == 2 if race < .
label define black 1 "black"                    ///
                   0 "non-black"
label value black black    

proprcspline marst grade, xlab(0(5)15)          ///
                          by(black, note(""))