Stata The Stata listserver
[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

re: st: interactions


From   David Airey <david.airey@vanderbilt.edu>
To   statalist@hsphsun2.harvard.edu
Subject   re: st: interactions
Date   Thu, 26 Jun 2003 10:58:45 -0500

Original question
> >> What's the easiest way to generate all [n-way] interactions
> >> when you have many continuous variables to predict a continuous
> >> response?

On Thu, 26 Jun 2003, David Airey wrote:
> I have not been able to use xi to create continuous*continuous
> interactions on the fly. I don't think xi does this from the
> description. It does cat*cont though.

Do cont*cont interactions make sense? It is often an act of faith that a
unit increase in X_i produces a Beta_i increase in Y and that the Betas
are additive. It seems wildly optimistic that a k increase in X_i
together with an l increase in X_j should give the same additional
increase as an l increase in X_i with a k increase in X_j.

This seems in general an approach based on having columns of figures so a
computer will always do the arithmetic, whether or not the sum is
justified.

I'm guilty of that last criticism.

Is the reason xi was designed to give the interactions it does based on any truth to your criticism?

-Dave

*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/




© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index