Extract values from 3'rd dimmenision with 2D matrix indices

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omri r 2019-10-23

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评论： omri r 2019-10-23

采纳的回答： Daniel

Hi,

Say I have 3D matrix (A), and 2D matrix (B) which each element is the third dimmesnions index I want to extract from A:

A = rand(3,3,3);

B = [1 1 1;

2 2 2;

1 2 3];

So if A is:

A(:,:,1) =

0.8147 0.9134 0.2785

0.9058 0.6324 0.5469

0.1270 0.0975 0.9575

A(:,:,2) =

0.9649 0.9572 0.1419

0.1576 0.4854 0.4218

0.9706 0.8003 0.9157

A(:,:,3) =

0.7922 0.0357 0.6787

0.9595 0.8491 0.7577

0.6557 0.9340 0.7431

Then the result C would be

C = [0.8147 0.9134 0.2785;

0.1576 0.4854 0.4218;

0.1270 0.8003 0.7431];

How can I find C in matlab?

Would very appreciate any help with that

Thanks in Advence!

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采纳的回答

Daniel 2019-10-23

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Hi omri,

hope this helps:

mult = zeros(3,3,3);
mult(:,:,:) = reshape([B==1,B==2,B==3],[3,3,3]);
A_1 = A .* mult;
C = sum(A_1,3)

Cheers,

Daniel

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Daniel 2019-10-23

在 MATLAB Online 中打开

In this case I would use a for-loop:

A_1 = zeros(768,1024,72);
for i=1:72
    A_1(:,:,i) = A(:,:,i) .* double(B==i);
end
C = sum(A_1,3);

omri r 2019-10-23

Works like a charm.

Thank you very much!

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