MATLAB: Find one-to-one correspondence with “knnsearch” function

Question

Hey everyone!

Is it possible to use the function Idx = knnsearch(X,Y) in order to get a one-to-one correspondence between X and Y? I would like to exclude all values that have been already matched with the nearest neighbor in Idx. If it's not, do you know another way to do that?

Thank you in advance.

Answer 1

Hi,

I understand that you are trying to find one to one correspondence between X and Y. One approach to find it using knnsearch is:-

load hospital;
X = [hospital.Age hospital.Weight];
tempX = X;
Y = [20 162; 30 169; 40 168; 50 170; 60 171];  
for i=1:size(Y,1)
    Idx = knnsearch(X,Y(i,:));
    tempX(Idx,:) = inf;
    id(i) = Idx;
end

Another approach is using pdist2 :-

load hospital;
X = [hospital.Age hospital.Weight];
Y = [20 162; 30 169; 40 168; 50 170; 60 171];  
D = pdist2(X,Y);
[D,I] = sort(D);
temp = zeros(size(D,1),1);
id = zeros(size(D,2),1);
for i=1:size(D,2)
    count = 1;
    while(temp(I(count,i))~=1 || id(i)==0)
        if temp(I(count,i))==0
            temp(I(count,i)) = 1;
            id(i) = I(count,i);
        else
            count = count+1;
        end
    end
end