MATLAB: Compute average in different columns of cell arrays without considering 0 values

Question

I have a cell array of 30 arrays. Each cell in it is a matrix of thousands rows and let's say several columns.

With a simple example, my cell is C and C{1,1} contains a matrix of single double values like this

C{1,1}=[1 4  5
        2 56 6 
        3 0 0]
C{2,1}=[1 0  0
        2 6  11
        3 0  0]

Also I want to get the mean of all non zeros elements in the 2nd columns in all the cell matrices

If I do

mean(C{1,1}(:,2)) %mean of 2nd column in first cell matrix

but this also includes values where 2nd column is 0 so to remove zero values I did in 3 steps

    A=C{1,1};
    B=A(:,2)>0;
    mean(A(B,2));

or in a single line

mean(C{1,1}(C{1,1}(:,2)>0,2))

So far, this is ok and gives me the average of a the second column in the first cell matrix but then when I wanted to get at once all the averages of the cell matrices and compute its means later with

Averages(:)= mean(C{:,1}(:,2))

but I get an error. I am not removing the zeros here just for the line to be more clear. My problem is how to use the : with the cell matrices. With a for loop, I can do it like this

Averages=zeros(30,1);
for ii=1:30
 Averages(ii)=mean(C{ii,1}(C{ii,1}(:,2)>0,2)); 
end
AvgC=mean(Averages);

But is there a way to do it without for. In other words how can access to the all cells 2nd column at once?

Answer 1

z = cat(3,C{:});
x = squeeze(z(:,2,:));
out = (sum(x)./sum(x~=0))';