CODEWITHSUNDEEP
matlabcell-array
niceman
niceman

Reputation: 2673

what's the fastest way to subtract two cell arrays in matlab

Pretend I have two cell arrays A and B, each element in those cells is N*M matrix, example :
A={ [2 3;4 5] [1 5;7 8]} and B={ [1 2;4 5] [7 9;10 1]} both are cells each element is 2*2 matrix.

Now I can subtract those cell arrays element-wise like this: 

C=cellfun(@minus,A,B,'UniformOutput',false);

this will result in C={[1 1;0 0] [-6 -4;-3 7]}.

Now is that the fastest way ? or is there a faster approach ?

Consider cells with large number of matrices each matrix is small.

Upvotes: 2

Views: 1640

Answers (2)

matlabgui
matlabgui

Reputation: 5672

As already mentioned a lot depends on the data, but in your example the fastest way is probably a nested for loop:

A={ [2 3;4 5] [1 5;7 8]};
B={ [1 2;4 5] [7 9;10 1]};
tic
C=cellfun(@minus,A,B,'UniformOutput',false);
toc
tic
s = size(A);
for ii=1:s(1)
  for jj=1:s(2)
    D{ii,jj} = A{ii,jj}-B{ii,jj};
  end
end
toc
isequal ( C, D )

output:

Elapsed time is 0.001420 seconds.
Elapsed time is 0.000017 seconds.

ans =

     1

Upvotes: 1

Luis Mendo
Luis Mendo

Reputation: 112679

You could convert to a 3D array, subtact, and convert back:

mat2cell(cat(3, A{:}) - cat(3, B{:}), size(A{1},1), size(A{1},2), [1 1]);

Of course it would be faster if you could avoid the conversions, that is, work with 3D arrays directly.

Upvotes: 3

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