Processing all subsets of a larger matrix

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Sean
Sean 2012-11-14
I have data in the form of MxNx3xK or MxNx3xKxJ types of matrices. If I wanted to use a function that takes an array of 3 values as an input (e.g. the entire third dimension of the matrix), does anyone know of a way to perform the function on the entire matrix?
The only way I know to do this is with nested for loops which is (or at least has been in earlier versions of matlab) very slow.
An simple example would be an image file that was 640x480x3 (where the third dimension contains RGB data). If I wanted to do a color transform on the whole image without going through pixel by pixel with nested loops, how could I do that?
Thanks in advance.
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Sean
Sean 2012-11-14
编辑：Sean 2012-11-14
Can you give me an indication of what wasn't clear? The question seems pretty straight forward (to me).
I added an example to go with the question in case that helps clarify things.
Image Analyst
Image Analyst 2012-11-14
It's not clear to me either. What is this? Is it a movie (or set of multiple movies) where k is the frame number, and j is the movie number? Or is it a volumetric color image where k is the slice number in the volume and J is a time point? Or is it something else? Why can't you just extract the color image and do the transform and then combine it into an output image?

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Matt J
Matt J 2012-11-14
out = cellfun(fun, num2cell(data,3), 'uni',0);
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Matt J
Matt J 2012-11-14
Instead of using CELL2MAT, use CAT and RESHAPE. Example:
A=rand(5,4,3,5,6);
B=cellfun(@(x) x(:)*x(:).' , num2cell(A,3), 'uni',0);
C=reshape(cat(3,B{:}),5,4,[],5,6);
>> Whos C
Name Size Kilobytes Class Attributes
C 5x4x9x5x6 43 double

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