MATLAB: How can i multiply two matrices

matrix

I have a matrix 'a' with size 3×3 and 'b' with size 3×1.i want to multiply the inverse of 'a' with matrix 'b'.I tried the below code but got an error "Matrix dimensions must agree". please help to solve this

    a=[1 0 -3; 2 -2 1; 0 -1 3];
    inv_a=inv(a);
    b=[0;2;121];
    c=inv_a.*b;

Best Answer

    c=inv_a * b;

not .*

inv_a is a 3 x 3 matrix, and you want algebraic matrix multiplication by the 3 x 1 matrix b in order to get the 3 x 1 solution.

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MATLAB: How to reorder cell array columns based on the order of a vector matrix, while keeping rows intact in Matlab

Would this work?

 >> buffer = arrayfun(@(rId) data(rId,order(rId,:)).', 1:size(order,1), ...
                      'UniformOutput', false) ;
 >> reordered_data = [buffer{:}].'
 reordered_data = 
    'B'    'B'    'B'    'B'    'B'    'A'    'A'    'B'
    'B'    'B'    'A'    'B'    'A'    'A'    'A'    'A'
    'A'    'A'    'B'    'A'    'A'    'B'    'B'    'B'
    'A'    'A'    'A'    'A'    'B'    'A'    'A'    'A'

MATLAB: Does matlab support parallelized loops on GPU

Scrap A = repmat(A,N,1) and instead repeat along dim 3. Then use pagefun.

A = repmat(A,1,1,N);
inv_A = pagefun(@mldivide, A, eye(6));

Or just use inv.

inv_A = pagefun(@inv, A);

However, you shouldn't ever be computing the inverse of a matrix, you should use mldivide to compute the solution to your linear system accurately for each output.

Best Answer

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MATLAB: How to reorder cell array columns based on the order of a vector matrix, while keeping rows intact in Matlab

MATLAB: Does matlab support parallelized loops on GPU

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