R function that duplicates Octave's poly function?
Cool. Is one of the results the definitive function to use to mimic Octave's poly function? There were about 10 returns, and none clearly identified themselves as the definitive functionality representing the poly capability, so any insight and clarification is appreciated. ----- Original Message ---- From: David Winsemius <dwinsemius at comcast.net> To: Jason Rupert <jasonkrupert at yahoo.com> Cc: R-help at r-project.org Sent: Sat, November 28, 2009 9:23:23 AM Subject: Re: [R] R function that duplicates Octave's poly function?
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