How to copy every 500 rows to a new variable?

Hi,

I have a [30000 x 57] matrix, I want to copy every new 500 rows to a new variable?

Thanks.

Answer 1

[Stephen23]

https://www.mathworks.com/help/matlab/matlab_prog/string-evaluation.html

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

[Ilham Hardy]

Wow, thanks for the concise explanation.

Now I am really convinced not to dynamically named variables.

Thanks Stephen :)

Answer 2

[Star Strider]

Another approach:

M = randi(9, 30000, 57);                                        % Create Data
Mr = reshape(M, 50, [], 57);                                    % Reshape
Mr = permute(Mr, [1 3 2]);                                      % Shuffle Dimensions
Mc = mat2cell(Mr, ones(size(Mr,1),1), size(Mr,2), size(Mr,3));  % Create Cell Array

Every element of ‘Mc’, from ‘Mc{1}’ to ‘Mc{50}’ is a different matrix variable. To convert them back into double arrays for calculations, use the cell2mat function.

[Bish Erbas]

Awesome!

[Star Strider]

Thank you!

My code does the same essential task yours does, just differently.

That brings to focus the observation that neither you nor I created 50 ‘new’ variables with our code, but instead created a single cell array with segments of the original matrix that are easier to access and work with, as ‘akshay raj’ essentially requested.

It would seem that reading and understanding the existing Answers would avoid much of the consternation that is too frequently apparent otherwise.

Answer 3

[Thorsten]

Why do you want to create 60 new variables and double the data? That's not a good idea. You can keep your original data and just address the i'th set of your 500 rows using

 ind = [1:500] + (i-1)*500;
 your_function(X(ind,:));

Answer 4

[Bish Erbas]

Do you really have to create individual variables for each 500 rows? This approach is not recommended because it is not using the array processing power of MATLAB. The preferred method is to store related data in a single array or a cell array. For example:

A = rand(30000,57);
N = (size(A,1)/500);
cellVar = cell(1,N);
for k = 1:N
  cellVar{k} = A(500*(k-1)+1:500*(k-1)+500,:);
end

Answer 5

[Walter Roberson]

result = squeeze(cellfun(@transpose, num2cell(reshape(YourMatrix.', size(YourMatrix,2), 500, []), [1 2]), 'uniform', 0));

This will give you a 60 x 1 cell array, each entry of which is a 500 x 57 array.