Divide large size matrixes, multiply the small matrixes and sum the results together.
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I divided two m x n matrixes A and B into several equal i x j matrices using mat2cell, respectively, and then I want to multiply the respective split matrixes and sum them together like
A11, … , A1j , ... Ai1, … , Aij are built from A, and
B11, … , B1j , ..., Bi1, … , Bij , are built from B,
What I want is
C = A11* B11 + … + Aij* Bij
Are there any commands in matlab can do this?
Many thanks!
4 Comments
Andrei Bobrov
on 18 May 2019
What you want, Elements multiplication or matrix multiplication in any case your formula will give an error:
>> A = rand(32, 32 );
B = rand(32, 32 );
A11_77 = mat2cell (A, [ 2 2 2 2 2 2 4 2 2 2 2 2 2 4 ] , [ 2 2 2 2 2 2 4 2 2 2 2 2 2 4] );
B11_77 = mat2cell (B, [ 2 2 2 2 2 2 4 2 2 2 2 2 2 4 ] , [ 2 2 2 2 2 2 4 2 2 2 2 2 2 4] );
>> A11_77{6,7} * B11_77{6,7}
Error using *
Incorrect dimensions for matrix multiplication. Check that the number of columns in the first matrix matches the number of rows
in the second matrix. To perform elementwise multiplication, use '.*'.
>> A11_77{1,1} * B11_77{1,1} + A11_77{7,7} * B11_77{7,7}
Matrix dimensions must agree.
>>
Answers (1)
Andrei Bobrov
on 18 May 2019
Edited: Andrei Bobrov
on 18 May 2019
C = sum(A.*B,'all')
for MATLAB < R2018b :
AB = A.*B;
C = sum(AB(:));
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