Find if two sparse matrix have 1 in same position

Hi everybody, I'm new here and new in use of matlab. I have two sparse matrix of different sizes and i want to know if both have 1 in position (x,y). There is a way to compare without make a comparison for each elements? (the matrix is a 10^7*10^7).

Answer 1

[Cedric]

Do you need something along this line?

% - Build small test case. 
A = sprand( 4, 5, 0.5 ) > 0 ;    % 4x5 sparse.
B = sprand( 4, 4, 0.5 ) > 0 ;    % 4x4 sparse.

% - Find intersect of matching locations of non-zero elements.
[A_r, A_c] = find( A ) ;
[B_r, B_c] = find( B ) ;
matching_rc = intersect( [A_r,A_c], [B_r,B_c], 'rows' )

Which outputs e.g.:

 >> A
 A =
  4×5 sparse logical array
   (4,1)      1
   (1,2)      1
   (1,3)      1
   (2,3)      1
   (4,4)      1
   (1,5)      1
   (2,5)      1

 >> B
 B =
  4×4 sparse logical array
   (2,1)      1
   (4,1)      1
   (2,2)      1
   (4,2)      1
   (1,4)      1
   (2,4)      1
   (4,4)      1

 >> matching_rc
 matching_rc =
     4     1
     4     4

[Lorenzo Lasagni]

thank you so much! It's exactly what i would to do!

[Cedric]

My pleasure!

Answer 2

[Cam Salzberger]

Hello Lorenzo,

Sparse matrices in MATLAB are nice because you can often treat them as regular matrices. Specifically, indexing still works just fine:

rng default % For repeatability
A = sparse(randi(2,10)-1);
B = sparse(randi(2,10)-1);
A(3, 8) == 1 && B(3, 8) == 1
A(3, 9) == 1 && B(3, 7) == 1

Hope this helps!

-Cam

[Lorenzo Lasagni]

The answer below is what i was looking for, thank you anyway!