trideigs.m

%  Find eigenvalues and eigen vectors of real symetric tridiagonal matrix
%  specified by main diagonal D and subdiagonal stored E one dimensional 
%  vectors.
%
%  [W] = trideigs(D,E) 
%  Find all eigenvalues.
%
%  [W,Z] = trideigs(D,E)
%  Find all eigenvalues and eigenvectors.
%
%  [W,Z] = trideigs(D,E,RANGE,VL,VU) 
%  Find all eigenvalues and eigenvectors in the half-open interval (VL,VU].
%
%  [W,Z] = trideigs(D,E,RANGE,IL,IU)
%  Find the IL-th through IU-th eigenvalues.