jacobi.m

学习matlab的朋友

function[x,many]=jacobi(A,b,x,tol)
% 雅可比迭代法用于计算线性方程组.
%   a为待解线形方程组的系数矩阵, b为常数矩阵,
%   x为一初始值, tol为计算精度

% 调用格式为:[x,many]=jacobi(A,b,x,tol) 
% x,tol 可省略
if nargin<=2 
    x=zeros(length(A),1);
    tol=1e-4; 
elseif nargin<=3
    tol=1e-4;    
end

D=diag(diag(A));
U=triu(-A,1);
L=tril(-A,-1);
hold on
for t=1:length(x)
    plot(t,x(t),'b^')
end
many=0;
while  true
  x0=x;  
  x=inv(D)*(U+L)*x+inv(D)*b;
  many=many+1;
  for t=1:length(x)
    plot(t,x(t),'bo')
  end
 
  if (norm(x0-x)<tol) && i<1000
      for t=1:length(x)
          plot(t,x(t),'r.')
      end
      break;
  end
end
  hold off