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st: Combining factor variable categories
From
Richard Williams <[email protected]>
To
[email protected]
Subject
st: Combining factor variable categories
Date
Fri, 13 Dec 2013 13:36:28 -0500
I have a friend who wants to combine categories in a factor variable,
e.g. 1, 2, 3 = 0, 4, 5 = 1. The challenge is that he wants to do
different combos within the same model, e.g. use the 5 category
version for main effects and a 2 category version for interactions.
He wants margins to work correctly so he doesn't want to first
compute different variables and then use them in the model, because
margins wouldn't know, for example, that the 5 category version was
related to the 2 category version.
I think you could do this via constraints, e.g. something like
webuse nhanes2f, clear
constraint 1 1b.health = 2.health
constraint 2 1b.health = 3.health
constraint 3 4.health = 5.health
logit diabetes i.health, constraint (1/ 3)
Is there some simpler way?
-------------------------------------------
Richard Williams, Notre Dame Dept of Sociology
OFFICE: (574)631-6668, (574)631-6463
HOME: (574)289-5227
EMAIL: [email protected]
WWW: http://www.nd.edu/~rwilliam
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