How to average over a cell-array of arrays?

arrays matlab mean cell-array
Tobias Kienzler picture Tobias Kienzler · Mar 4, 2011 · Viewed 34.9k times · Source

I have a cell array c of equal-sized arrays, i.e. size(c{n}) = [ m l ... ] for any n. How can I get the mean values (averaging over the cell array index n) for all array elements in one sweep? I thought about using cell2mat and mean but the former does not add another dimension but changes l to l*n. And looping manually of course takes like forever...

Answer

gnovice picture gnovice · Mar 4, 2011

If all of your arrays are the same size, it makes more sense to store them in a matrix rather than a cell array. That makes it easier to perform operations across them, like taking the mean. You can convert your data to a matrix using the functions NDIMS and CAT:

dim = ndims(c{1});          %# Get the number of dimensions for your arrays
M = cat(dim+1,c{:});        %# Convert to a (dim+1)-dimensional matrix
meanArray = mean(M,dim+1);  %# Get the mean across arrays

Related questions

How do I iterate through each element in an n-dimensional matrix in MATLAB?

I have a problem. I need to iterate through every element in an n-dimensional matrix in MATLAB. The problem is, I don't know how to do this for an arbitrary number of dimensions. I know I can say for i = 1:…

Read More
size of NumPy array

Is there an equivalent to the MATLAB size() command in Numpy? In MATLAB, >>> a = zeros(2,5) 0 0 0 0 0 0 0 0 0 0 >>> size(a) 2 5 In Python, >>> a = zeros((2,5)) >>> array([[ 0., 0., 0., 0., 0.], [ 0., 0., 0., 0., 0.]]) >>> ?????

Read More
How can I efficiently remove zeroes from a (non-sparse) matrix?

I have a matrix: x = [0 0 0 1 1 0 5 0 7 0]; I need to remove all of the zeroes, like so: x = [1 1 5 7]; The matrices I am using are large (1x15000) and I need to do this multiple times (5000+), so efficiency is key!

Read More