multiplying 2 matrices with difference sizes

Hello all,

I have a 12x16 matrix, M,

      [ 0     0     1     0     0     0     0    -1     0     1     0     0    -1     0     0     0;0     0     0     1     0     0     1     0     0     0     0     0    -1     0     1     0;0    -1     0     0    -1     0     1     0     0     1     0     0     0     0     0     0;0     0     0     1     0    -1     0     0     0     0     1     0     0     1     0     0;0     0     1     0     0     0     0     0    -1     0     0     0     0     0     1     1;1     0     0     0     0    -1     0     0     0     1     0     0     0     0     1     0;0     0     0     1     0     0     0    -1    -1     0     0    -1     0     0     0     0;0    -1     0     0     0    -1     0     0     0     0     0    -1     0     0     0     1;1     0     0     0     0     0     1     0     0     0     0     0     0     1     0     1; 0     0     1     0    -1     0     0     0     0     0     0    -1     0     1     0     0; 0    -1     0     0     0     0     0     0    -1     0     1     0    -1     0     0     0;1     0     0     0    -1     0     0    -1     0     0     1     0     0     0     0     0]

and a 12x4 matrix P,

   [0.8033 - 0.5956i  -0.4224 - 0.9064i  -0.7512 + 0.6600i  -0.6502 - 0.7597i; -0.9993 + 0.0363i  -0.9690 + 0.2473i   0.8134 + 0.5817i  -0.7593 - 0.6507i; 0.6407 + 0.7678i  -0.4739 - 0.8806i  -0.9973 - 0.0735i   0.3493 + 0.9370i;  0.7352 + 0.6778i   0.9006 + 0.4346i  -0.9478 + 0.3189i   0.9575 + 0.2883i;-0.1797 + 0.9837i   0.7638 - 0.6455i   0.6129 + 0.7902i  -0.7013 + 0.7129i;0.8619 - 0.5071i  -0.9843 + 0.1766i  -0.3126 + 0.9499i  -0.8056 + 0.5925i;-0.8067 + 0.5910i   0.4202 - 0.9074i   0.7392 - 0.6735i   0.6508 - 0.7592i;-0.8884 - 0.4590i  -0.5747 - 0.8183i   0.8557 + 0.5174i   0.5900 - 0.8074i;-0.9836 + 0.1801i  -0.3134 + 0.9496i   0.8707 - 0.4919i   0.6079 - 0.7940i; -0.8750 - 0.4841i  -0.9497 + 0.3131i  -0.8134 - 0.5817i   0.9811 - 0.1937i;-0.3354 + 0.9421i   0.5805 - 0.8143i  -0.2518 + 0.9678i  -0.8530 + 0.5218i;-0.6454 - 0.7638i  -0.9661 + 0.2582i   0.6314 + 0.7755i   0.4847 - 0.8747i]

where the number of columns in P is the same as the number of non-zero elements in each row of M. I would like to multiply each row of M (non-zero elements) with a row of P in a fast way. Can someone help me please? Thank you!

Answer 1

[Roger Stafford]

   A = M.';
   A = (reshape((A(A~=0)),4,12).').*P; % The element-by-element product

This of course depends on each row of M having exactly four nonzero elements. Otherwise you will receive error messages. I assume you meant element-by-element multiplication.

[Mnr]

Thank you!