How to find out the location difference of nonzero entries in two sparse matrices?

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Hello, All,
I have two sparse matries which have the same size. I know every nonzero entry in A must correspond to a nonzero entry in B, but some of nonzero entries in B which correspond to zero entries in A. For example, A=[0 1 0 2;3 0 0 4;0 5 6 0]; B=[0 1 0 2;3 7 0 4;8 5 6 0]. I want to find out the location of nonzero entries in B which correspind to zero entries in A. The answer to this example is: (2, 2) and (3, 1). Their correspinding entries are 7 and 8 in B.
Thanks.
Benson

Accepted Answer

Stephan
Stephan on 23 Feb 2019
Hi,
this are not sparse matrices. However you find the locations given as row and column values and the corresponding values with:
A=[0 1 0 2;3 0 0 4;0 5 6 0];
B=[0 1 0 2;3 7 0 4;8 5 6 0];
[row, col] = find(A~=B)
vals = B(A~=B)
results in:
row =
3
2
col =
1
2
vals =
8
7
which is exactly the desired result.
Best regards
Stephan
  2 Comments
Benson Gou
Benson Gou on 24 Feb 2019
Hi, Stephan,
Thanks for your response. It is very good. How about the following example?
A=[0 1 0 2;3 0 0 4;0 5 6 0];B=[0 2.43 0 1.09;4.97 7.30 0 3.3;8.03 5.43 9.12 0];
The locations of nonzero entries in A and B are the same (but their values are different) except (2,2) and (3,1), their values are 7.30 and 8.03.
Our real case is like this. Thanks a lot for your great help.
Benson

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