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Using find in a 3d matrix in MATLAB.

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felix on 3 Feb 2011
Commented: Rik on 11 Sep 2017
I have a 3D Matrix such as
QQ(:,:,1) =
1 2
3 4
QQ(:,:,2) =
5 6
7 8
now i want to use
[r c]=find(QQ,8) r=max(r) c=max(c)
to find my position for point 8. 'find' just works for 2D arrays .for the 3D case it doesnt work. is there is possibility for 3D arrays?
Kenneth Eaton
Kenneth Eaton on 3 Feb 2011
I think you have a typo in your code. If you're looking for the position of the value 8, you should do FIND(QQ == 8). The second input to FIND isn't the value you're looking for, it's the *number of indices* to find.

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Accepted Answer

Kenneth Eaton
Kenneth Eaton on 3 Feb 2011
When finding values in multidimensional (i.e. greater than 2-D) arrays using the function FIND, it is best to get a single linear index from FIND then convert it to subscripts using the function IND2SUB. Here's how you can find the position of 8 in your 3-D matrix:
[r,c,v] = ind2sub(size(QQ),find(QQ == 8));
Rik on 11 Sep 2017
I wrote up a function that does this for the general case. It works with the same syntax as the built-in find, but it also supports multidimensional matrices. You can find it on the File Exchange. Then you can simply run:

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