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Consider two matrices A (2times4) and B (4times3). Write a MATLAB script to calc

ID: 3564835 • Letter: C

Question

Consider two matrices A (2times4) and B (4times3). Write a MATLAB script to calculate the product C = AB. Create the product matrix C before you begin the calculation. Write your script in terms of matrix entries cij, aij and bij as described in class. Recall that each element in the product matrix is the dot product of the rows in the first matrix with the columns in the second matrix or, as an equation, cij = aikbkj where n is the inner dimension when forming the product AB. Test that the inner dimensions are correct before performing the calculation. If the inner dimensions are not correct display an error and stop. Note that the script should be general and thus should be able to perform the product for any A of dimension 2times4 and B of dimension 4times3 specified by the user. Show that your script works by computing the product AB for A = B =

Explanation / Answer

A=[3 4 1;
    2 3 4];

B=[ 1 2 3;
     4 5 6;
     7 8 9];

[nRow1,nCol1]=size(A);
[nRow2,nCol2]=size(B);

if nCol1 ~= nRow2
    error('inner dimensions must match');
end

C = zeros(nRow1,nCol2);

for i = 1:nRow1
     for j = 1:nCol2
         for k = 1:nCol1
             C(i,j) = C(i,j) + A(i,k)*B(k,j);
         end
     end
end

C
-------------------------

This gives

C =

     26 34 42
     42 51 60

To verify

A*B

ans =

     26 34 42
     42 51 60