Comparing two Matrix for similar elements

suppose you run a check between two matrix, like c=0; if A(1,1) == B (1, 1:3) c=c+1; else c=0; end and the output(ans) is (true, true, false) , I mean (1 1 0).

my counter(c) should run twice(if if A(1,1), B(1,1) and B(1,2) is equal to 8) but it will show c=0. I need C = 2

Other way I found is - Count only when it is true, like

if A(1,1) == B(1,1) c=c+1; else c=0; end

but in the second case, i have to do it for all B elements, and that's not good for big matrix. how to check and count?

[Andrei Bobrov]

Please attach your matrices A and B storing in mat - file.

[Jan]

The question is not clear:

c=0;
if A(1,1) == B (1, 1:3)
 c=c+1; 
else 
 c=0;
end

Note that A(1,1) == B (1, 1:3) replies a vector, but if requires a scalar condition. Therefore Matlab inserts an all() implicitely.

 and the output(ans) is (true, true, false) , I mean (1 1 0).

The shown code does not have any output. It replies either c=1 or c=0, but not [1,1,0].

 my counter(c) should run twice(if if A(1,1), B(1,1) and B(1,2)
 is equal to 8)

I cannot folow you here.

Answer 1

[Andrei Bobrov]

c = nnz(A(:)' == B(:)); % MATLAB >= R2016b
c = nnz(bsxfun(@eq, A(:)', B(:)));  % MATLAB <= R2016a

[Daniel Brower]

Does this check if A is similar to B?

[Walter Roberson]

Only in the sense that some objects cannot be compared. For example if A is object class tf (transfer function) and B is object class primitive chart line, then you would get an error message. But the code would be fine with A being double and B being character for example.

The original question implied that the array sizes are not the same, so the code should not be checking that they are the same.

[Daniel Brower]

I mean if A is an nxn matrix of real numbers and B is an nxn matrix of real numbers, how would I check if A and B are similar matrices to each other, in the sense that B=S^-1*A*S.

Answer 2

[Jan]

Does only A(1,1) occur in your porblem? Then:

c = (A(1,1) == B)

or if the number of equal elements is wanted

c = sum(A(1,1) == B)    % or nnz() instead of sum()

If all elements of A are concerned, see either Andrei's solution, or:

c = sum(ismember(A(:), B(:))  % Or B(:), A(:) ?

[Zeina Abdullah]

@Jan can you help me by answer my question in my profile please . i am tring to find similar problem but I did not find

[Walter Roberson]

https://www.mathworks.com/matlabcentral/answers/1623080-how-to-find-relationship-between-two-or-more-matrix?s_tid=srchtitle appears to be the reference