RPQR79(3)

SYNOPSIS
SUBROUTINE RPQR79 (NDEG, COEFF, ROOT, IERR, WORK)

NAME
rpqr79 - Find the zeros of a polynomial with real coefficients.

LIBRARY
SLATEC

CATEGORY
F1A1A

TYPE
SINGLE PRECISION (RPQR79-S, CPQR79-C)

KEYWORDS
COMPLEX POLYNOMIAL, POLYNOMIAL ROOTS, POLYNOMIAL ZEROS

AUTHOR
Vandevender, W. H., (SNLA)

DESCRIPTION
Abstract This routine computes all zeros of a polynomial of degree NDEG with real coefficients by computing the eigenvalues of the companion matrix. Description of Parameters The user must dimension all arrays appearing in the call list COEFF(NDEG+1), ROOT(NDEG), WORK(NDEG*(NDEG+2)) --Input-- NDEG degree of polynomial COEFF REAL coefficients in descending order. i.e., P(Z)= COEFF(1)*(Z**NDEG) + COEFF(NDEG)*Z + COEFF(NDEG+1) WORK REAL work array of dimension at least NDEG*(NDEG+2) --Output-- ROOT COMPLEX vector of roots IERR Output Error Code - Normal Code 0 means the roots were computed. - Abnormal Codes 1 more than 30 QR iterations on some eigenvalue of the companion matrix 2 COEFF(1)=0.0 3 NDEG is invalid (less than or equal to 0)

REFERENCES
(NONE)

ROUTINES CALLED
HQR, XERMSG

REVISION HISTORY (YYMMDD)
800601 DATE WRITTEN
890505 REVISION DATE from Version 3.2
891214 Prologue converted to Version 4.0 format. (BAB)
900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ)
911010 Code reworked and simplified. (RWC and WRB)