MATLAB: Find matrix in cell matrix

find cel matrix

hello,

i have cell matrix size(1*1000) each element is matrix (10*10)

i want to test if matrix is an element of cell or not how to do it?

Best Answer

index = [];
for k = 1:numel(C)
  if iseuqal(C{k}, test_matrix)
     index = k;
     break;
  end
end

Or if you need all occurrences:

index = false(1, numel(C));
for k = 1:numel(C)
  if isequal(C{k}, test_matrix)
     index(k) = true;
  end
end
found = find(index);  % Or use the logical index vector directly

A shorter form:

found = find(cellfun(@(c) isequal(c, test_matrix), C));

At least under R2009a, the for loop method is 6 times faster for finding a 10x10 matrix in a 1 x 1000 cell array. cellfun is nice, but slow.

Related Solutions

MATLAB: How to split a [30x250x1000] array into 1,000-2D matrices

Just use a simple cell array:

function epoch = matrix_extractor(data_class,number_epochs)
    data_class;
    C = cell(1,number_epochs);
    for k = 1:number_epochs
        C{k} = data_class(:,:,k);
    end
end

Note that writing this is a waste of time: just use num2cell or mat2cell.

Note that there is likely little point to this anyway: it would be simpler to just access the original data array using indexing, rather than splitting up and duplicating that data in memory. Splitting up data rarely makes processing data easier.

MATLAB: Concatenate arrays within a loop,

Easy, given any number of arrays in a cell array C. You could use a loop like this, although it is inefficient because the output array is not preallocated:

C = {[1,2],[3,4],...} % cell array of arrays.
A = C{1};
for k = 2:numel(C)
    A = [A;C{k}];
end

Simpler and more efficient would be to concatenate them all at once, without a loop, e.g.:

A = vertcat(C{:})

Whatever you do, do NOT try to access variable names dynamically in a loop! Read this to know why:

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

Using an array (e.g. a cell array) and indexing is much simpler, neater, much more efficient, less buggy, and easier to debug.

Best Answer

Related Solutions

MATLAB: How to split a [30x250x1000] array into 1,000-2D matrices

MATLAB: Concatenate arrays within a loop,

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