[R] R function that duplicates Octave's poly function?

[David Winsemius]

On Nov 28, 2009, at 9:33 AM, Jason Rupert wrote:

>
> By any chance is anyone aware of an R function that duplicates  
> Octave's poly function?
>
> Here is a description of Octave's poly function:
>
> Function File:  poly (A)
>     If A is a square N-by-N matrix, `poly (A)' is the row vector of
>     the coefficients of `det (z * eye (N) - a)', the characteristic
>     polynomial of A.  As an example we can use this to find the
>     eigenvalues of A as the roots of `poly (A)'.
>          roots(poly(eye(3)))
>          => 1.00000 + 0.00000i
>          => 1.00000 - 0.00000i
>          => 1.00000 + 0.00000i
>     In real-life examples you should, however, use the `eig'
>     function for computing eigenvalues.
>
>     If X is a vector, `poly (X)' is a vector of coefficients of the
>     polynomial whose roots are the elements of X.  That is, of C is a
>     polynomial, then the elements of `D = roots (poly (C))' are
>     contained in C.  The vectors C andD are, however, not equal due
>     to sorting and numerical errors.
>
> Thanks again for any insights and feedback.

RSiteSearch("characteristic polynomial")

>
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT