% gauss_el.m
% Gauss Elimination to solve A*x = b
% input : A, b
% output : x
%Programmed by Jo, Hyun-Ho
%function x = gauss_el(A,b);
A = myrand(10,10,1,9), b = myrand(10,1,1,5)
n = length(A);
R = [A b];
for j=1:n-1
for i=j+1:n
if R(j,j)==0
max_id = find( max( abs(R(j+1:n,j)) ) ) + j; % Find pivot
temp = R(j,:); % Change two rows
R(j,:) = R(max_id,:);
R(max_id,:) = temp;
end
a = R(i,j)/R(j,j);
R(i,:) = R(i,:) - a*R(j,:);
end
end
% 역대입법
A = R(:,1:n); b = R(:,n+1);
x = zeros(n,1);
for j=n:-1:1
x(j) = ( b(j) - A(j,j+1:n)*x(j+1:n) )/A(j,j);
end
norm( b-A*x )
%%%%
A =
5 3 3 7 3 5 5 2 6 3
9 8 1 8 9 6 9 1 3 5
2 4 5 5 7 3 8 9 9 5
1 3 2 2 2 5 3 7 2 3
7 3 5 9 6 3 3 3 8 4
3 9 1 8 8 8 9 5 4 3
7 5 4 4 1 7 1 5 3 5
1 1 4 9 6 1 4 4 5 4
4 6 9 7 5 5 1 5 2 4
1 4 9 2 3 9 4 1 7 7
b =
2
3
3
4
2
4
2
4
1
4
ans =
4.8700e-014
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김대식105424 gauss_el
gauss-el
