program define points
        version 4.0

        local x = "`1'"
        local y = "`2'"

        tempvar xp yp sp

        gen `xp' = $AX * `x' + $BX
        gen `yp' = $AY * `y' + $BY
        gen `sp' = 100

        gph vpoint `yp' `xp' `sp'

end