How to input this Gauss-seidel problem into the following code( code might need work)

Question

steven butera 2020-2-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/507130-how-to-input-this-gauss-seidel-problem-into-the-following-code-code-might-need-work

编辑： Pravin Jagtap 2020-2-26

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4. Use Gauss-Seidel iteration to solve the following band system.

12x1 − 2x2 + x3 = 5

− 2x1 + 12x2 − 2x3 + x4 = 5

x1 − 2x2 + 12x3 − 2x4 + x5 = 5

x2 − 2x3 + 12x4 − 2x5 + x6 = 5

...

x46 − 2x47 + 12x48 − 2x49 + x50 = 5

x47 − 2x48 + 12x49 − 2x50 = 5

x48 − 2x49 + 12x50 = 5

clc; % helps in clearing screen
clear; % helps in clearing history
clear all; % helps in closing files if any
%Function for page 167 question 4.
function X=gseid(A,B,P,delta, max1)
%Input - A is an N x N nonsingular matrix
%- B is an N x 1 matrix
%- P is an N x 1 matrix; the initial guess
%- delta is the tolerance for P
%- max1 is the maximum number of iterations
%Output - X is an N x 1 matrix: the Gauss-Seidel
%approximation to the solution of AX = B
N = length(B);
for k=1:max1
for j=1:N
if j==1
X(1)=(B(1)-A(1,2:N)*P(2:N))/A(1,1);
elseif j==N
X(N)=(B(N)-A(N,1:N-1)*(X(1:N-1))')/A(N,N);
else
%X contains the kth approximations and P the (k-1)st
X(j)=(B(j)-A(j,1:j-1)*X(1:j-1)'-A(j,j+1:N)*P(j+1:N))/A(j,j);
end
end
err=abs(norm(X'-P));
relerr=err/(norm(X)+eps);
P=X';
if(err<delta)|(relerr<delta)
break
end
end
X=X';
    
    %%%%%%%%%%%%%%% End of Code %%%%%%%%%%%%%%

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Answer 1

Pravin Jagtap 2020-2-26

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/507130-how-to-input-this-gauss-seidel-problem-into-the-following-code-code-might-need-work#answer_417416

编辑：Pravin Jagtap 2020-2-26

Hello Steven,

I am assuming that you are using the code written by someone else for your homework question. For your problem, construct the input arguments(A, B, P, delta, max1) from your system of equations. Representation of input arguments is given in the code. Refer the following link for understanding how to use functions and how to pass the arguments in MATLAB.

https://www.mathworks.com/help/matlab/matlab_prog/create-functions-in-files.html