ROOT2POLY Function

Forms a polynomial from a given set of roots.

Usage

result = ROOT2POLY(r)

Input Parameters

r—A one-dimensional array or scalar containing the polynomial roots.

Returned Value

result—A one-dimensional array containing the coefficients of the polynomial.

Keywords

None.

Discussion

Given a set of roots r₀, r₁, r₂, ..., r_N, ROOT2POLY determines the coefficients of the polynomial A(x) where A(x) is given by:

 

                                           = a₀ + a₁x + a₂x² + ... + a_Nx^N  , a_N = 1

ROOT2POLY always returns a polynomial with a_N normalized to 1.

Example

In this example, ZEROPOLY is used to first compute the roots of the polynomial A(x) given by

A(x) = 3 + 2x + 12x² + 4x³ + x⁴

ROOT2POLY is then used to reproduce A(x) from its roots.

A = [3, 2, 12, 4, 1]

r = ZEROPOLY(A)

PM, ROOT2POLY(r), Format = '(f10.1)'

; 3.0

; 2.0

; 12.0

; 4.0

; 1.0

See Also

ZEROPOLY