left and right sides have a different number of elements

Question

Jacob 2023-3-21

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1932980-left-and-right-sides-have-a-different-number-of-elements

编辑： Torsten 2023-3-22

im trying to solve a gauss-seidel method problem and im getting the "left and right sides have a different number of elements" error in the xn(Iter) lines. how do i fix this?

A = [10 -2 -5 30; -2 15 -5 -5; -5 -5 14 25]
C = [2 ; 1 ; 3]
Error = 100;
Thr = 1;
Iter = 0;
x1 = C(1,1);
x2 = C(2,1);
x3 = C(3,1);
while Iter<5
    Iter = Iter+1;
    x1(Iter) = (A(1,4) - A(1,2)*x2 - A(1,3)*x3)/A(1,1);
    x2(Iter) = (A(2,4) - A(2,1)*x1 - A(2,3)*x3)/A(2,2);
    x3(Iter) = (A(3,4) - A(3,1)*x1 - A(3,2)*x2)/A(3,3);
    x1 = x1(Iter);
    x2 = x2(Iter);
    x3 = x3(Iter);
    
end

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Torsten 2023-3-22

编辑：Torsten 2023-3-22

You cannot use x1,x2 and x3 as a scalar and simultaneously as an array. Make up a decision for one of the two ways.

And what about x4 ? Your matrix A is 3x4 ! I've never heard of Gauss-Seidel for non-square systems...

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Answer 1

Matt J 2023-3-22

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1932980-left-and-right-sides-have-a-different-number-of-elements#answer_1198335

编辑：Matt J 2023-3-22

在 MATLAB Online 中打开

A = [10 -2 -5 30; -2 15 -5 -5; -5 -5 14 25];
C = [2 ; 1 ; 3];
Error = 100;
Thr = 1;
Iter = 0;
x1 = C(1,1);
x2 = C(2,1);
x3 = C(3,1);
while Iter<5
    Iter = Iter+1;
    X1(Iter) = (A(1,4) - A(1,2)*x2 - A(1,3)*x3)/A(1,1);
    X2(Iter) = (A(2,4) - A(2,1)*x1 - A(2,3)*x3)/A(2,2);
    X3(Iter) = (A(3,4) - A(3,1)*x1 - A(3,2)*x2)/A(3,3);
    x1 = X1(Iter);
    x2 = X2(Iter);
    x3 = X3(Iter);
    
end
X1,X2,X3
X1 = 1×5
    4.7000    4.6152    5.1480    5.2490    5.4178
X2 = 1×5
    0.9333    1.2457    1.5479    1.6460    1.7589
X3 = 1×5
    2.8571    3.7976    3.8789    4.1771    4.2482