I have problem with while loop.

So I have homework about Gaussian Elimination, when input matrix b I want to ensure that the input matrix has the same number of rows as matrix A and it must be in a column matrix so I tried these code with while loop:

A=input('Input matrix A');
b=input('Input matrix b in column form');
szA=size(A)
szb=size(b)
while (szb(1,1)~=szA(1,1) && szb(1,2)~=1)
    b=input('Matrix b is not in column form,please re-input');
    szb=size(b)
    if (szb(1,1)==szA(1,1)&& szb(1,2)==1)
    break
    end
end
Ab=[A b]

My goal here is when the input matrix b has a different number of rows than that of matrix A and/or the number of columns is not equal to 1 then the user has to re-enter the matrix. When both conditions are met then break the while loop and continue.

But when I tested with matrices like:

A=[1 2;2 1] b=[1 2;2 1]

The while loop still break and give me matrix Ab.

Or

A=[1 2;2 1] b=[1;2;3]

The while loop breaks and the program gives me the horzcat error (I understand that matrix b don't have the same number of rows as matrix A will cause this error)

Please help. Thank you.

Answer 1

[Chunru]

Make the following change:

%while (szb(1,1)~=szA(1,1) && szb(1,2)~=1)
while (szb(1,1)~=szA(1,1) || szb(1,2)~=1)

[Tran Thien]

It works! Thank you very much.

[Chunru]

To make your code easer to read, you can chnage szb(1,1) to szb(1) and so on.