MATLAB: A question about sorting a vector

Question

Suppose I have a column vector V of length N and I map every element in V to an element y in Y so, we have a column vector Y of length N.

Suppose I want to sort Y in an ascending order and pick r elements from the vector V that corrosponds to the least r values in Y.

I thought of:

V; Y;
N; r;
[Ys idx]=sort(Y);
for i=1:r
    Best(i)=V(idx(Ys(i)))
end
Best(i)

So is this correct?

Answer 1

It does not look correct to me, specifically because ‘Ys’ may not necessarily be an integer greater than 0, as required for subscript references in MATLAB, and also within the size limits of ‘V’. (We have no idea what ‘Y’ is, since you have not told us.)

This may give you the result you want, however you have not told us that, either. It nevertheless avoids the explicit loop:

V = randn(10,1);                            % Create Vector

Y = randn(10,1);                            % Create Vector
[Ys, idx]=sort(Y);
r = 5;                                      % Choose A Value
Best = V(idx(1:r))                          % Result