?? eigen.m
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function [L,X]=eigen(K,M,b)% [L]=eigen(K,M)% [L]=eigen(K,M,b)% [L,X]=eigen(K,M)% [L,X]=eigen(K,M,b)%-------------------------------------------------------------% PURPOSE% Solve the generalized eigenvalue problem% [K-LM]X = 0, considering boundary conditions.%% INPUT:% K : global stiffness matrix, dim(K)= nd x nd% M : global mass matrix, dim(M)= nd x nd% b : boundary condition matrix% dim(b)= nb x 1% OUTPUT:% L : eigenvalues stored in a vector with length (nd-nb) % X : eigenvectors dim(X)= nd x nfdof, nfdof : number of dof's%-------------------------------------------------------------% LAST MODIFIED: H Carlsson 1993-09-21% Copyright (c) Division of Structural Mechanics and% Department of Solid Mechanics.% Lund Institute of Technology%------------------------------------------------------------- [nd,nd]=size(K); fdof=[1:nd]';% if nargin==3 pdof=b(:); fdof(pdof)=[]; if nargout==2 [X1,D]=eig(K(fdof,fdof),M(fdof,fdof)); [nfdof,nfdof]=size(X1); for j=1:nfdof; mnorm=sqrt(X1(:,j)'*M(fdof,fdof)*X1(:,j)); X1(:,j)=X1(:,j)/mnorm; end d=diag(D); [L,i]=sort(d); X2=X1(:,i); X=zeros(nd,nfdof); X(fdof,:)=X2; else d=eig(K(fdof,fdof),M(fdof,fdof)); L=sort(d); end else if nargout==2 [X1,D]=eig(K,M); for j=1:nd; mnorm=sqrt(X1(:,j)'*M*X1(:,j)); X1(:,j)=X1(:,j)/mnorm; end d=diag(D); [L,i]=sort(d); X=X1(:,i); else d=eig(K,M); L=sort(d); end end%--------------------------end--------------------------------?? 快捷鍵說明
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