3D Array Multiplication with 2D Matrix

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Anum Ahmed
Anum Ahmed 2019-8-28
回答： stav marzuk 2021-12-7
Hi,
I have a 3D array of lets say 500:10:32 elements. I want to multiple the first dimension of lthis array with another 1:500 matrix. How would I do this?
Regards
  2 个评论
Bob Thompson
Bob Thompson 2019-8-28
Which 500 elements from the first matrix do you want to multiply the second matrix by? There are 320 different options.
Or are you looking to multiply all 320 sets of 500 against the new matrix?
Also, how are you looking to store your new 500 x 500 matrices?
Anum Ahmed
Anum Ahmed 2019-8-28
I am trying to perform the element wise multiplication of the 3D array with a second 2D array and getting the 3D array as a result where lets say row elements would be multiplied with another matrix.

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采纳的回答

KALYAN ACHARJYA
KALYAN ACHARJYA 2019-8-28
编辑：KALYAN ACHARJYA 2019-8-28
data1=rand(500,10,32);% 3D Array
data2=rand(1,500); %1x500 mat
result=data1(1:500,1,1)*data2; %Multiplication
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显示 2更早的评论
Bob Thompson
Bob Thompson 2019-8-28
Also, if you want to perform the multiplication on the entire 3D array, then the first thing that comes to mind for me is for loops, or arrayfun. There might be a way to do it without loops, but I don't know it (which doesn't say much).
for i = 1:size(data1,2)
for j = 1:size(data1,3)
data1(:,i,j) = data1(:,i,j).*data2';
end
end

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更多回答（3 个）

Bruno Luong
Bruno Luong 2019-8-28
编辑：Bruno Luong 2019-8-28
Simply do (R2016b or later)
data1 = data1 .* data2(:)
  2 个评论
Bob Thompson
Bob Thompson 2019-8-28
编辑：Bob Thompson 2019-8-28
Does this automatically choose the appropriate dimension though? I would logically make the connection between 500 and 500 elements in a dimension, but that doesn't mean a computer will.
Or will it produce 500 500x10x32 arrays, one for each element of data2?
Bruno Luong
Bruno Luong 2019-8-28
Yes, the length of 500 of the first dimension must match. That's all.

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Anum Ahmed
Anum Ahmed 2019-8-28
Thanks all..!!!
stav marzuk
stav marzuk 2021-12-7
Hi i think i have the same problem, but i didnt sucssed to solve it.
I have an rgb photo with the size: 30432 29516 3
and i have a mask bw with the size 30432 29516
is it possible to multiply the two of them?
rgb .*bw
this multplication is not working, is there a solution?
Thanks in advance

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