How to make a graph for U-shaped relationships

[Sang-Bum Park]

Hi,

I often check estimated relationships in a graph by using the Stata marginsplot or marginscontplot command.
Can these commands also produce a graph in terms of a U-shaped (or inverted-U-shaped) relationship?
Or is there any other command in Stata?

[Joseph Coveney]

Yes. See below for example.

version 15.1

clear *

set seed `=strreverse("1495462")'
quietly set obs 25

generate double x = runiform() - 0.5
generate double y = rnormal(x * x, sqrt(0.005))

*
* Begin here
*
regress y c.x##c.x

quietly margins , at(x = (-0.5(0.05)0.5))
marginsplot , ///
    plotopts(lcolor(black) msize(small) mfcolor(white)) ///
    noci ///
    xlabel(-0.5(0.1)0.5) ///
    ylabel( , angle(horizontal) nogrid) ///
    title("")

exit

[Sang-Bum Park]

Joseph Coveney I am very grateful for your excellent answer.