How to use arrayfun or cellfun on m x n x o matrix where it performs operation on each m x n matrix

Hi,

Please let me preface my question by stating my intent. My goal here is for work flow automation and to reduce code, not for execution speed.

I have in this case a standard RGB image which consists of an mxnxo matrix, of which o is size 3. Therefore there are 3 mxn matrices in which each represents intensity values of the respective R,G,and B channels. I wish to use array fun in this case, to return a 3 element cell array that contains the histcounts inside of each cell element for the respective channels in my image.

Another more generic way to think about this is; I want to perform a function on each mxn in my mxnxo matrix. Rather than to index each one R = (:,:,1) G = (:,:,2) B = (:,:,3)....histcounts( R ) histcounts(G) histcounts(B).

The problem I have is the syntax for this in arrayfun or cellfun. e.g. arrayfun(@histcounts,img(:,:,?))

Thanks in advance, Chris

Answer 1

[Matt J]

out = arrayfun( @(i) histcounts(img(:,:,i)),  1:3, 'uni',0)

[Chris Knab]

Exactly it, thanks man!

[Matt J]

Of course, a simple for-loop would work fine, too

for i=1:3
 out{i}=histcounts(img(:,:,i));
end

[Chris Knab]

Of course, in my case I was interested in the syntax you provided as it can be used in many other scenarios I come across. I am often working in lives scripts trying to prototype some analysis and accessing data this way with less code is much cleaner.

Thanks!