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Consider the case of multiplying three matrices with A*B*C, where A is 500-by-2, B is 2-by-500, and C is 500-by-2. With no parentheses, the order of operations is left to right so A*B is calculated first, which forms a 500-by-500 matrix.
Instead of doing a matrix multiply, we can multiply the corresponding elements of two matrices or vectors using the .* operator.
22 paź 2015 · Explanation: Here is an example. ⎛ ⎜⎝4 5 3 4 1 2⎞ ⎟⎠(3 1 0 3) Find the first row of the product. Take the first row of ⎛ ⎜⎝4 5 3 4 1 2⎞ ⎟⎠, and make it vertical. (We'll do the same for the second row in a minute. And then for the third row.) 4 5(3 1 0 3)
You can add one or more elements to a matrix by placing them outside of the existing row and column index boundaries. MATLAB automatically pads the matrix with zeros to keep it rectangular. For example, create a 2-by-3 matrix and add an additional row and column to it by inserting an element in the (3,4) position.
16 lis 2009 · You can do this in one line using the functions NUM2CELL to break the matrix X into a cell array and CELLFUN to operate across the cells: Z = cellfun(@(x) x*Y,num2cell(X,[1 2]),'UniformOutput',false); The result Z is a 1-by-C cell array where each cell contains an A-by-D matrix.
Matrix multiplication is associative, so you can do it in whichever order you like. You can prove it by writing the matrix multiply in summation notation each way and seeing they match.
To multiply a matrix by a single number is easy: These are the calculations: We call the number ("2" in this case) a scalar, so this is called "scalar multiplication". Multiplying a Matrix by Another Matrix. But to multiply a matrix by another matrix we need to do the "dot product" of rows and columns ... what does that mean?
