How can i find indices of constant elements between 2 arrays?

Hi, i have 2 enormous matrices A and B which are parameter relevant. With find() function i know which elements are non zero and with find(A-B) i know which elements are changed due to parameter. But how can i find out the indices of elements which remain constant?

[KSSV]

Can you give a small exampl of what you want?

[Dyuman Joshi]

Use find( (A-B) == 0) ?

[Jiahong Zou]

Yeah sure. For example,

A = [1 2 0; 0 1 0; 5 0 8]

A = 3×3

1 2 0 0 1 0 5 0 8

B = [ 1 3 0; 0 4 0; 5 0 6]

B = 3×3

1 3 0 0 4 0 5 0 6

How to find the indices of bold 1 and 5 ? Zero elements must be not included, because i tried

[row_zero, column_zero] = find(~(A - B))

row_zero = 6×1

1 2 3 3 1 2

column_zero = 6×1

1 1 1 2 3 3

And it directly went out of memory.

[Image Analyst]

Exactly how big are your arrays? Hundreds of millions of elements or more?

Answer 1

[the cyclist]

Do you mean the non-zero elements that are the same between the two arrays?

A = [1 2 0; 0 1 0; 5 0 8];
B = [1 3 0; 0 4 0; 5 0 6];

[r,c] = find(A==B & A~=0)

r = 2×1

1 3

c = 2×1

1 1

[Jiahong Zou]

Thanks!