# A question about sorting a vector

4 views (last 30 days)
Cantor Set on 7 Sep 2019
Commented: Cantor Set on 8 Sep 2019
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?
##### 2 CommentsShowHide 1 older comment
Cantor Set on 8 Sep 2019
A part of a homework problem.
Thank you!

Star Strider on 7 Sep 2019
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