build a matrix from cell

Dear

I have a cell array which I need to select only first column of each cell separately and put it into a matrix. But each column has different number of row.

can somebody help me ? I think I can build a matrix of zero with the size of my cell and then I put each column separately. However, following effort does not work.

[n,m]=size(X)
A = zeros(100,n);

for i=1:n
    A (:,n) = X{n}(:,1)
end

Answer 1

[Azzi Abdelmalek]

X={magic(4),eye(4),rand(4)}    % Example
y=cell2mat(cellfun(@(x) x(:,1),X,'un',0))

[Niki]

Thanks but That is not working for when we have your example X but transposed

X={magic(4),eye(4),rand(4)} % example
X=X';

Now I want to get the first column of each cell into a matrix

[Azzi Abdelmalek]

 y=cell2mat(cellfun(@(x) x(:,1)',X,'un',0))'

[Niki]

Again thanks but as I explained from very beginning the row of each column is not equal, by running that one I get this error

??? Error using ==> cat
  CAT arguments dimensions are not consistent.

    Error in ==> cell2mat at 85
                m{n} = cat(1,c{:,n});

Answer 2

[Azzi Abdelmalek]

X={magic(5);eye(4);rand(6)}
m=numel(X);
n=max(cellfun(@(x) size(x,1),X));
out=zeros(n,m);
for k=1:m
  a=X{k}(:,1);
  out(1:numel(a),k)=a;
end

[Niki]

are you sure this works correctly ? seems like this is a loop forever :-( do you have any other idea which works faster? my laptop is working for 10 min and still not finished

[Azzi Abdelmalek]

What is the size of X?

[Niki]

[n,m]=size(peaks)

n =

          8300

m =

       1