Sum the elements in cell array with different element length

Hi everyone,

I need to calculate the sum of elements in a cell array per column. I'm assuming that the cell is 4x4 and each element in it is a row vector with random length. In order to be able to sum the column I need to check the longest vector and pad all the other cell elements with nans or zeros. Here is what I did:

trial = cell(4,4);

trial{1,1} = [1 1 0 0 1 1 0 0];

trial{1,2} = [2 2 2 0 0 0 2 2 2 0 0 0];

trial{1,3} = [3 3 3 3 0 0 0 0 3 3 3 3 0 0 0 0];

trial{1,4} = [4 4 0 0 4 4 0 0];

trial{2,1} = [9 9 0 0 0 9 9 0 0 0 ];

trial{2,2} = [1 1 0 0 1 1 0 0];

trial{2,3} = [2 2 2 0 0 0 2 2 2 0 0 0];

trial{2,4} = [5 5 5 5 5 5 5 5 5 5];

trial{3,1} = [8 8 8 8 0 0 8 8 8 8];

trial{3,2} = [4 4 4 0 0 0 4 4 4 0 0 0];

trial{3,3} = [4 4 4 0 0 0 4 4 4 0 0 0];

trial{3,4} = [6 6 6 6];

trial{4,1} = [1 1 0 0 1 1 0 0];

trial{4,2} = [2 2 2 0 0 0 2 2 2 0 0 0];

trial{4,3} = [3 3 3 3 0 0 0 0 3 3 3 3 0 0 0 0];

trial{4,4} = [7 7 7 0 0 7 7 7];

for i = 1:4

for j = 1:4

trial = trial{i,j}; % dimension is 1xN

if length(trial{i,j})< 10

pad = nan(1,10-length(trial));

trial = [trial pad];

end

trial{i,j} = trial;

end

end

I'm getting the following error: Cell contents reference from a non-cell array object.

And I want to make the threshold (10 here) dynamic depending on the largest length in the column.

Thanks.

Answer 1

[Andrei Bobrov]

m = cellfun(@numel,trial);
k = num2cell(max(m(:))-m);
out = cellfun(@(x,y)[x(:); nan(y,1)]',trial,k,'un',0);

EDIT

out = sum(cellfun(@sum,trial));

or

m = cellfun(@numel,trial);
k = num2cell(max(m(:))-m);
SUM_out = cellfun(@(x,y)[x(:); zeros(y,1)]',trial,k,'un',0);
out = sum(cat(1,SUM_out{:}));

[Yasmin Tamimi]

Thank you! I just did a slight modification: k = num2cell(max(m(:)) - m); and I padded with zeros instead of nans to be able to sum the values up. So now I have trial{16x16} with each cell element 1x16. When I want to add them up I wrote: Sum_columns = cellfun(@sum ,out); But I ended up having Sum_columns{16x16} with each cell element is the summation of all the vector values for that cell. What I want is that for each column of out I need to do element by element summation and the end result will be 1x16

[Yasmin Tamimi]

Using it in this form will also add up the value the of cell elements column-wise but for all, I just specified the the number of rows and it worked! out = sum(cat(1,SUM_out{1:4})); Thanks a lot!