legroots.m

来自「matlab6矩阵微分工具 matlab6矩阵微分工具」· M 代码 · 共 12 行

function r = legroots(N);

%  The function r = legroots(N) computes the roots of the 
%  Legendre polynomial of degree N.

%  J.A.C. Weideman, S.C. Reddy 1998.

n = [1:N-1];                   %  Indices
d = n./sqrt(4*n.^2-1);         %  Create subdiagonals
J = diag(d,1)+diag(d,-1);      %  Create Jacobi matrix
r = sort(eig(sparse(J)));      %  Compute eigenvalues