# n-dimensional matrix - Store the indexes of the n-th dimension in n-th cell

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dave on 12 Sep 2013
I have a n-dimensional matrix M. Now I'm looking for a way to create a 1xn cell array, where the index vector of the n-th dimension of M is stored in the n-th cell.
So for example: If the size of M were 40x30x50x20, the resulting cell array should look like this:
myCell = {[1:40], [1:30], [1:50], [1:20]};
How would I do this?

Louis Vallance on 12 Sep 2013
Edited: Louis Vallance on 12 Sep 2013
If M is explicitly defined then could you do
vect = size(M); % vect = [40 30 50 20] in your example of M
%{
dim = length(vect); So that we know how many cells there will be.
For your example dim == 4;
%}
myCell = cell(1, dim); % Pre-allocate for speed (thanks for reminding me, Jan!)
for i = 1:dim
myCell{i} = 1:vect(i); % assign a 1 x vect(i) array to each cell
end
The value of myCell after running this code is:
>> myCell
myCell =
[1x40 double] [1x30 double] [1x50 double] [1x20 double]
I hope this helps!
Louis
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Jan on 12 Sep 2013
And for efficiency a pre-allocation is recommended:
myCell = cell(1, dim);