How to find correlations of corresponding rows of two arrays?

I have 2 arrays --- d1 and d2. d1 = [ 3 4 5 6 7 ; 8 9 10 11 12 ; 13 14 15 16 17 ]; and d2 = [ 18 19 20 21 22 ; 23 24 25 26 27 ; 28 29 30 31 32 ]. How do I find the correlation of each corresponding row? For example, what is the correlation of the first row of d1 ( [ 3 4 5 6 7 ] ) to the first row of d2 ( [ 18 19 20 21 22 ] ). Similarly, what are the two coefficients for the other two corresponding rows?

I tried the following code:

[r, pV]=corr(d1,d2,'rows','complete');

But it seems to return the coefficient of each cell with respect to all the cells. In this case, I want only 3 integers returned (each for each corresponding row). Any ideas on achieving this? Appreciate your assistance!

Answer 1

[Dave B]

The correlations of columns are the diagonal of the correlation matrix, so you can

• Transpose your matrices on the way in to corr, because you want rows not columns
• Use diag to get the diagonal specifically out of the matrix

d1 = rand(3,5);
d2 = rand(3,5);
C=corr(d1',d2')

C = 3×3

-0.2127 0.6956 0.0173 -0.6065 0.9023 0.4460 0.1537 -0.4428 -0.0161

diag(C)

ans = 3×1

-0.2127 0.9023 -0.0161

% Check that it's the same result as taking the correlations of each row
% indpendently
[corr(d1(1,:)',d2(1,:)') corr(d1(2,:)',d2(2,:)') corr(d1(3,:)',d2(3,:)')]'

ans = 3×1

-0.2127 0.9023 -0.0161

[Rabeca Mohammed]

Thank you so much!!