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Re: st: Graph Quadratic Term


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Graph Quadratic Term
Date   Mon, 18 Apr 2011 18:00:50 +0100

I don't know what you mean by "does not plot correctly" and in any
case you give very little code.

-predict- is a command, not a function.

This example may help

sysuse auto
gen headroomsq = headroom^2
logit foreign headroom headroomsq
predict predict, pr
scatter foreign headroom || mspline predict headroom

A quadratic on the logit scale naturally translates to a bell-shape on
the original scale.

Nick

On Mon, Apr 18, 2011 at 5:36 PM, Dennis Kramer <dkramerii@gmail.com> wrote:

> I am having trouble graphing the quadratic relationship between my
> outcome dependent and independent variable. I am currently modeling a
> -logit- function with my outcome being 0/1 for passing a standardized
> test. When I run my --logit-- with the sq term in the model I get a
> significant quadratic function; however, when I use the -- predict, pr
> -- function to plot for predictions the quadratic function does not
> plot correctly... could you provide some insight.
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