find matrix in cell 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?

[amina KHARBACHE]

i was lloking for simple insttruction with matlab who find directly the matrix inside the cell matrix

but with a simple loop for can do it

for i=1numel(cellmatrix) if cellmatrix{1,i}==test_matrix save_index=i; break end end

thanx in advance ^^

Answer 1

[Jan]

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.

[amina KHARBACHE]

i was lloking for simple insttruction with matlab who find directly the matrix inside the cell matrix

but with a simple loop for can do it

for i=1numel(cellmatrix) if cellmatrix{1,i}==test_matrix save_index=i; break end end

thanx in advance ^^

*************************

i already found it with loop for

thank you so much ^^

[Jan]

Do not use == for the comparison, because it works elementwise. It returns a matrix with TRUE for all equal elements, but Matlab's IF expects a scalar. Therefore internally this is evaluated:

if (all(cellmatrix{1,i}(:) == test_matrix(:)) && ~isempy(cellmatrix{1.i})

Better use isequal as in the code I've posted to avoid any ambiguities.

Note: To my surprise this seems to be slightly slower:

index = false(1, numel(C));
for k = 1:numel(C)
  index(k) = isequal(C{k}, X);
end
m = find(index);

Answer 2

[Rik]

Have you tried ismember?

[amina KHARBACHE]

yes it didn't work with me