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Re: st: Interaction with Squared Term

From   Richard Williams <>
Subject   Re: st: Interaction with Squared Term
Date   Tue, 25 Oct 2011 17:10:19 -0500

At 01:48 PM 10/25/2011, Ryan Goodstein wrote:

I am trying to estimate a multinomial logit specification that
includes a categorical variable interacted with a squared term.

> mlogit dq60 invPS##c.o_ltv##c.o_ltv ageq ageq2

Stata (v11) gives me the following error:

> invalid interaction specification;
> multiple 'o' operators attached to a single variable are not allowed within an
> interaction specification{p_end}

I saw a post on this on Stata List from 2009 which says this bug will
be fixed in an update
(, but I
haven't been able to find an update.  Has this bug been fixed?

I assume you actually updated your Stata. If so, the comment about "o operators" makes me wonder if Stata is getting confused by your variable names. Try creating a clone of o_ltv (e.g. ltvo) and see if the problem persists.

Richard Williams, Notre Dame Dept of Sociology
OFFICE: (574)631-6668, (574)631-6463
HOME:   (574)289-5227
EMAIL:  Richard.A.Williams.5@ND.Edu

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