Margins plots curve lines other than straight line

[Vill Wang]

After using "margins" command, I use "marginsplot" command to graph the margins plots. I get straight line while I find in some other papers, they present curve. How can I get curves other than straight lines?

The graph I get like this:




The graph in other papers like this:


Thanks.

[Joseph Coveney]

After using "margins" command, I use "marginsplot" command . . . I get straight line while I find in some other papers, they present curve. How can I get curves other than straight lines?

Add a polynomial or spline interaction to the model.

sysuse auto

// Straight lines
regress price i.foreign##c.mpg
margins foreign, at(mpg = (10 15 20 25 30 35 40))
marginsplot

// Curves
regress price i.foreign##c.mpg##c.mpg
margins foreign, at(mpg = (10 15 20 25 30 35 40))
marginsplot

[Vill Wang]

Add a polynomial or spline interaction to the model.

sysuse auto

// Straight lines
regress price i.foreign##c.mpg
margins foreign, at(mpg = (10 15 20 25 30 35 40))
marginsplot

// Curves
regress price i.foreign##c.mpg##c.mpg
margins foreign, at(mpg = (10 15 20 25 30 35 40))
marginsplot

Thanks a lot for your generous help!

When I use command

xi: probit y x $controla , vce (cluster StockName1)

I get the plot like this:




However, other papers' plots are curve.


Thanks

[Joseph Coveney]

A quick-and-dirty example:

sysuse auto
probit foreign c.mpg

// Curved
margins , at(mpg = (10(10)40))
marginsplot

// Straight
margins , at(mpg = (0(0.001)0.004))
marginsplot

Depending upon where you are, you can get a straight-seeming line or an curved line with marginsplot after margins with the default (probability) predictions after probit, logit.

[Vill Wang]

[QUOTE]
A quick-and-dirty example:
Code:
sysuse auto probit foreign c.mpg // Curved margins , at(mpg = (10(10)40)) marginsplot // Straight margins , at(mpg = (0(0.001)0.004)) marginsplot
Depending upon where you are, you can get a straight-seeming line or an curved line with marginsplot after margins with the default (probability) predictions after probit, logit.


Thanks a lot for your help!