% R_MOD Modified recurrence coefficients.
%
% Given a weight function w through the first Nmax recurrence
% coefficients ab of its orthogonal polynomials, [abmod,Ncap,
% kount]=R_MOD(N,ab) generates the first N recurrence
% coefficients abmod of the modified weight function w/p, where
% p is the polynomial of degree M defined by Eq.(3.1.75)
% incorporating the M poles selected. Their negative reciprocals
% (the quantities zeta_mu in Eq.(3.1.71)) must be provided
% in the first column of the global Mx2 array Z, the second
% column containing the respective multiplicities. It is assumed
% that complex poles occur in conjugate complex pairs and that
% both poles of each pair are included in the array Z. Other
% global parameters are mc, mp, iq,idelta, irout, AB, eps0, Nmax,
% and M, which are used in the routine MCDIS called by R_MOD, and
% have the meaning explained there. Be sure that the variables
% ab, M, Z are declared global variables in the quadrature routine
% QUADRAT. The output variables Ncap and kount are inherited from
% the routine MCDIS with meanings explained there. The alpha- and
% beta-coefficients of the given weight function are contained in
% the first and second column of the Nmax x 2 input array ab,
% those of the modified weight function in the first and second
% column of the Nx2 output array abmod.
%
% See also MCDIS.
%
function [abmod,Ncap,kount]=r_mod(N,ab)
global mc mp iq idelta irout AB Z eps0 Nmax M
global theta c
if size(ab,1)0
[abmod,Ncap,kount]=mcdis(N,eps0,@quadrat,Nmax);
else
Ncap=0; kount=0; abmod(1:N,:)=ab(1:N,:);
end