program define segments
        version 4.0

        local x1 = "`1'"
        local y1 = "`2'"
        local x2 = "`3'"
        local y2 = "`4'"

        tempvar xp1 xp2 yp1 yp2

        gen `xp1' = $AX * `x1' + $BX
        gen `yp1' = $AY * `y1' + $BY
        gen `xp2' = $AX * `x2' + $BX
        gen `yp2' = $AY * `y2' + $BY


/*

        scalar i=1
        while i<= _N {

                local xx1=`xp1'[i]
                local xx2=`xp2'[i]
                local yy1=`yp1'[i]
                local yy2=`yp2'[i]

                gph line `yy1' `xx1' `yy2' `xx2' 1

                scalar i=i+1}  */

        gph vseg `yp1' `xp1' `yp2' `xp2'

end