%  The script file orrsom.m computes the eigenvalues of the Orr-Sommerfeld%  equation using NxN Chebyshev differentiation matrices.% S.C. Reddy, J.A.C. Weideman 1998N = input(' Order of the differentiation matrix: N = ? ');R = input(' Reynolds number: R = ? ');i = sqrt(-1);[x,DM] = chebdif(N+2,2);                       % Compute second derivative    D2 = DM(2:N+1,2:N+1,2);                    % Enforce Dirichlet BCs                                     [x,D4] = cheb4c(N+2);                          % Compute fourth derivative     I = eye(size(D4));                        % Identity matrixA = (D4-2*D2+I)/R-2*i*I-i*diag(1-x.^2)*(D2-I); % Set up A and B matricesB = D2-I;e = eig(A,B);