# Using 3D array to subtract row Q from row P

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Sara Foster on 7 Sep 2019
Commented: Sara Foster on 7 Sep 2019
If I have a test array e.g C = [100,100,100;50,50,50;40,40,40] and I use the command P = C(1,1,:), it will give me a value of 100 (which is the first P1 pixel) and using Q = C(3,1,:) it gives me a value of 40.
However I want to use an example function like this to calculate distance between pixels:
P = P(1); P2 = P(2); P3 = P(3);
Q = Q(1); Q2 = Q(2); Q3 = Q(3);
squaredDistance = (P1-Q1)^2 + (P2-Q2)^2 + (P3-Q3)^2;
And P1 and Q1 using squared distance formula only gives me a value of 3600, where I want total squared distance using P2 and P3 & Q2 and Q3 is there any way of doing this without needing to resort to for loops? Thanks!

James Tursa on 7 Sep 2019
Edited: James Tursa on 7 Sep 2019
It is unclear what you really want. If you want the Euclidean distance squared between rows, e.g., rows 1 and 3, then just
d = C(1,:) - C(3,:);
result = d * d';
Sara Foster on 7 Sep 2019
If I'm using P and Q as input commands, I want to use any row value for these two inputs e.g. I could have Q = C(3,1,:) or Q = C(2,1,:) depending on the input I choose for Q, as my inputs are P and Q and output is the distance.