channelflow.org

% A script file to solve the following 5 x 5 system 
%
%
%       c f1 + f2  =  0
%  f2 - 2 f3 + f4  =  5
%       f1 + c f3  =  4
%     3 f1 + 7 f5  = -1
%       f2 - c f4  =  2
%
% where c = sqrt(2);
%
% Rewrite this as an Ax=b problem, or Af=b. 
% 
% c  1  0  0  0    f1      0
% 0  1 -2  1  0    f2      5
% 1  0  c  0  0    f3  =   4
% 3  0  0  0  7    f4     -1
% 0  1  0 -c  0    f5      2
 
% Here's a slick way to enter the above matrix
 
c = sqrt(2);
A = zeros(5,5);
 
A(1, [1 2]) = [ c 1 ];
A(2, [2 3 4]) = [ 1 -2 1 ];
A(3, [1 3]) = [ 1 c ];
A(4, [1 5]) = [ 3 7 ];
A(5, [2 4]) = [ 1 -c ];
 
b = [0 5 4 -1 2]';
 
f = A\b;