sort and group vectors in a matrix

I have two matrices of a size of 125x3. Lets say matrix X and Y. I am calculating cartesian distances between X(1,1) with all the rows of Y. So the code looks like below,

L = length(X);

for i=1:L

X(i)= sqrt((X(1,3)-Y(i,3))^2 + (X(1,4)-Y(i,4))^2 + (X(1,5)-Y(i,5))^2);

X = X/10;

B = sort(X);

B = B';

end

I am now trying to get the distances between all of X's elements with Y's element and sort and save them in a bigger matrix of 125x125. So I am trying to create another loop that saves the data in sucessive columns, but somehow I am not able to do that.

Answer 1

[Star Strider]

This is a bit confusing.

I would use the pdist2 function for this —

x = rand(1,5);
y = rand(10,5);

X = x(3:5)

X = 1×3

0.1281 0.5614 0.6284

Y = y(:,3:5);

D = pdist2(X, Y)

D = 1×10

0.4898 0.7704 0.8340 0.3424 1.0069 0.6262 0.5756 0.9131 0.5587 0.3489

[Dsort,I] = sort(D(:))

Dsort = 10×1

0.3424 0.3489 0.4898 0.5587 0.5756 0.6262 0.7704 0.8340 0.9131 1.0069

I = 10×1

4 10 1 9 7 6 2 3 8 5

The sort call sorts the vectors and returns the sorted vector and the original indices of the corresponding element.

I do not see where a matrix of distances would be used here, because this compares one vector to a matrix. A matrix would be appropriate for comparing two matrices, as described in Compute Euclidean Distance.

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