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Re: st: RE: -prgen- with a quadratic function

From   Nick Winter <>
Subject   Re: st: RE: -prgen- with a quadratic function
Date   Tue, 15 Mar 2005 21:20:58 -0500

Also, my -oprobpr- can do this; it is available from SSC.

--Nick Winter

At 10:03 PM 3/15/2005 +0000, you wrote:
I don't think Scott Long is a member of Statalist.

No matter: your problem should yield to -adjust-
followed by an appropriate graph.


Mariano Sana

> Hi Statalisters.  Someone experienced with ?prgen- might be
> able to answer this.
> I ran a logit model that has, among its predictor variables,
> AGE and AGESQ.
> The coefficient for AGE is positive and the coefficient for AGESQ is
> negative.  The turning point is at age 79 or so.  I?ve been trying to
> generate a graph that shows how predicted probabilities vary
> by age for a few groups in my analysis.  I used the ?prgen- command from
> the Spostado package.
> The graph that I get doesn?t make sense. The probability
> increases nonstop
> and becomes asymptotic to 1 at age 90 or so.
> I realize that the problem is that ?prgen- cannot vary the
> value of AGESQ
> as the value of AGE varies.  The default for AGESQ is the
> mean of AGESQ,
> unless I specify another value.  Obviously, I need AGESQ to
> be the square of AGE as AGE varies.
> By now I think I have no other solution than running
> ?prvalue- (also from
> the Spostado package) multiple times to get the probabilities
> I need for
> the graph. Or is there any other way? Is this a question for
> Scott Long?

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