Concatenate cell array inside a cell array

My cell array is of different size. I want to convert it to the matrix. I added NAN to make the size equal but I found NAN added inside a cell array like the picture [1*481]. I try to horzcat it but did not work. Can anyone help me, please?

Answer 1

[Voss]

C = {rand(1,7),rand(1,4),rand(1,3)};
disp(C);

    {[0.9714 0.8038 0.7325 0.4787 0.1328 0.8788 0.6320]}    {[0.1632 0.6340 0.3939 0.5810]}    {[0.8846 0.5465 0.3481]}

num = cellfun(@numel,C);
N = numel(C);
M = NaN(N,max(num));
for ii = 1:N
    M(ii,1:num(ii)) = C{ii};
end
disp(M);

    0.9714    0.8038    0.7325    0.4787    0.1328    0.8788    0.6320
    0.1632    0.6340    0.3939    0.5810       NaN       NaN       NaN
    0.8846    0.5465    0.3481       NaN       NaN       NaN       NaN