R help - Jul 2012 - Specify model with polynomial interaction terms up to degree n

I would like to specify a model with all polynomial interaction terms between
two variables, say, up to degree 6. For example, terms like a^6 + (a^5 *
b^1)  +  (a^4 * b^2) + ... and so on.  The documentation states

The ^ operator indicates crossing to the specified degree.

so I would expect a model specified as y ~ (a+b)^6 to produce these terms.
However doing this only returns four slope coefficients, for Intercept, a,
b, and a:b.  Does anyone know how to produce the desired result? Thanks in
advance.

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On Jul 2, 2012, at 9:29 AM, YTP wrote:
> I would like to specify a model with all polynomial interaction  
> terms between
> two variables, say, up to degree 6. For example, terms like a^6 +  
> (a^5 *
> b^1)  +  (a^4 * b^2) + ... and so on.  The documentation states
>
> The ^ operator indicates crossing to the specified degree.
>
> so I would expect a model specified as y ~ (a+b)^6 to produce these  
> terms.
> However doing this only returns four slope coefficients, for  
> Intercept, a,
> b, and a:b.  Does anyone know how to produce the desired result?  
> Thanks in
> advance.
You might try:

poly(a,6)*poly(b,6)

(untested   ... and it looks somewhat dangerous to me.)

-- 
David Winsemius, MD
West Hartford, CT