sysuse auto
summarize price
local X = r(mean)
summarize mpg
local Y = r(mean)
scatter mpg price
twoway (scatter mpg price) (scatteri `Y' `X')
twoway (scatter mpg price) (scatteri `Y' `X' (6) "Grand Mean")
twoway (scatter mpg price) (lfit mpg price)(scatteri `Y' `X' (6) "Grand Mean")
twoway (scatter mpg price) (qfit mpg price)(scatteri `Y' `X' (6) "Grand Mean")