I am struggling to plot iteration vs error in the matlab code? can anyone help me with this? very much appreciate it.

This is the code for Jacobi iteration method. i wanted to plot iteration vs error. but i couldn't figure out how to do it?

% Jacobi method for linear equation
function[x,rel_error]=jacobimethod(A, b, x0, tol, iteration)
% Inputs: A - Coefficient matrix
A=[2 -1 0;-1 2 -1;0 -1 2];
%         b - Input matrix
b = [0; 2; 0];
x0=[0; 0; 0];
%       tol - Defining tolerance for solution
tol=1.e-03;
% iteration - Number of iterations
iteration=10;
% Outputs: x - Solutions
%  rel_error - Relative error
D = diag(diag(A));   % Making coefficient matrix diagonal
R = A - D;          % Construction of another matrix "R"
N = 1;               % iteration counter
x = x0;
rel_error = tol * 2; % norm(x - x0)/norm(x);
exct = A\b;
% Implementation of Jacobi method to solve Ax = b
while (rel_error>tol && N <= iteration)
    xprev = x;   
    x = inv(D)*(b - R*xprev);
    rel_error = norm((x - xprev)/x);
    er = norm(x-exct)
    fprintf('\n Iteration %i: Relative error =%d ',x, rel_error);   
    N = N + 1;       
end

Answer 1

[Torsten]

% Inputs: A - Coefficient matrix
A=[2 -1 0;-1 2 -1;0 -1 2];
% b - Input matrix
b = [0; 2; 0];
% x0  - Initial guess
x0 = [0; 0; 0];
% tol - Defining tolerance for solution
tol=1.e-03;
% iteration - Number of iterations
iteration=10;
[x,Rel_error]=jacobimethod(A, b, x0, tol, iteration);
x

x = 3×1

0.9688 1.9375 0.9688

plot(Rel_error)

% Jacobi method for linear equation
function[x,Rel_error]=jacobimethod(A, b, x0, tol, iteration)
% Outputs: x - Solutions
%  rel_error - Relative error
D = diag(diag(A));   % Making coefficient matrix diagonal
R = A - D;          % Construction of another matrix "R"
N = 1;               % iteration counter
x = x0;
rel_error = tol * 2; % norm(x - x0)/norm(x);
exct = A\b;
% Implementation of Jacobi method to solve Ax = b
while (rel_error>tol && N <= iteration)
    xprev = x;   
    x = inv(D)*(b - R*xprev);
    rel_error = norm(x - xprev)/norm(x);
    Rel_error(N) = rel_error;
    er = norm(x-exct);
    %fprintf('\n Iteration %i: Relative error =%d ',N, rel_error);   
    N = N + 1;       
end
end

[Uma Maheswara Rao Epuganti]

Hey thank you so much for immediate reply.

But there is no plot code here.

[Torsten]

Better ?

[Uma Maheswara Rao Epuganti]

Thank you. i do want to plot this for the first 10 iterations. this is only for 10th iteration. could you please tell me how to figure that out?

[Walter Roberson]

It looks to me as if the full plot is present in Torsten's answer.

Answer 2

[Walter Roberson]

fprintf('\n Iteration %d: Relative error = %g\n', N, rel_error);

[Uma Maheswara Rao Epuganti]

Hey thanks for the immediate reply.

But i do want to plot first 10 iterations with errors.