st: creating polynomial expansion

[Kit Baum <baum@bc.edu>]

Rafa said

What I am doing is to create the variables: x^2 , x^3 , z^2 and z^3  
and then
I am creating all possible interactions (without including those ones  
within
the same variable, e.g. x * x^2). In a second step I regress these  
variables
against "y". The procedure gets quite unmanageable with three  
variables and
higher order polynomials.

I am wondering if there is a code that generates the variables of the
polynomial expansion, or if there is a way to program this (perhaps  
there is
something in Mata that I am not aware of).



The code for whitetst (ssc type whitetst.ado) does something quite  
similar for squares and cross-products (including the pruning  
necessary if your varlist includes, e.g., x and x^2). You could  
readily adapt it to handle cubes.


Kit Baum, Boston College Economics
http://ideas.repec.org/e/pba1.html


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