How to create doubles from cell arrays?

I would like to ask if there is a more efficient code to do the following task:

a = cell(10,1); 

for i = 1 : 10
a{i,1} = randn(200,5);
end

for j =1:5
b{j} = [a{1,1}(:,j) a{2,1}(:,j) a{3,1}(:,j) a{4,1}(:,j) a{5,1}(:,j)];
end

Thank you!

Answer 1

[Guillaume]

if there is a more efficient code

Yes, don't use cell arrays!

a = randn(200, 5, 10);

your b{j} is simply

permute(a(:, j, :), [1 3 2])
%or
squeeze(a(:, j, :))

Even simpler, move the j to the third dimension

a = randn(200, 10, 5);
%b{j} would simply be  a(:, :, j)

[gsourop]

The initial matrices are of this form, I just use randn values in order to replicate the experiment. It is not that I am now starting the calculations. So I have to achieve result 'b' given the form of 'a'.

[Guillaume]

Yes, I also used randn purely for demonstration.

Don't use cell arrays if you don't have to. It complicates everything. Since the matrices in your cell array are all the same concatenate them into a 3D matrix and use that from then on.

%a: a cell array of MxN matrices;

bettera = permute(cat(3, a{:}), [1 3 2])

From then on, whenever you wanted to use b{j}, use

bettera(:, :, j)

It is even possible that whatever you wanted to do with each b{j] could be done at once on bettera.