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st: RE: varlist not allowed in xi3

From   "Nick Cox" <>
To   <>
Subject   st: RE: varlist not allowed in xi3
Date   Fri, 24 Apr 2009 14:27:37 +0100

-xi3- is a user-written command from the UCLA website. Please remember
to say where user-written commands you refer to come from. 

Your first need is to make more precise what Stata is complaining about.
Is "Stata" here the program -xi3- or is it -glm- or is yet something
else that either calls? Using -set trace on- (start with -set tracedepth
1-) may help to clarify the precise problem. 

At worst, you could just avoid -xi3- and calculate the interactions
yourself and see if that makes any difference. 

Either way, programs are not like electric appliances in your house,
which may just stop working (capriciously, as it may seem)!  


Dan Waldo

I am trying to test the nested interactions of 4 variables (n, a, g, and
s) on the depvar drg_wgt using xi3 and glm.

Stata tells me the following:

. xi3: glm drg_wgt i.n*i.a*i.g i.a*i.g*i.s [pweight=weight] , f(gamma)
i.n               _In_0-2             (naturally coded; _In_0 omitted)
i.a               _Ia_0-65            (naturally coded; _Ia_45 omitted)
i.g               _Ig_1-2             (naturally coded; _Ig_1 omitted)
i.s               _Is_1-7             (naturally coded; _Is_4 omitted)
varlist not allowed

The code works with a 3-way term and a 2-way term, but not with 2 3-way
terms. Stata should be disregarding the duplicate 2-way interactions;
all 4 explanatory variables are numeric (byte); and the drg_wgt is a
floating-point number. What am I missing? (What worries me is that I
thought this same code had run back in January, and this now casts doubt
on my memory of other events in that month.)

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