distance between array entries

How do you write code to get which of the entries stored in an array it is closest to for each data point?

For example:

array: [4 9 7 3 10 19 2 11]

and you want to find which entry each entry is closest to. So, in the above array, the answer would be:

[4 5 2 1 2 8 4 5]

(the number 4 is closest in value to the 4th entry in the array...the number 9 is closest in value to the 5th entry in the array...etc.)

[Jos (10584)]

You should define " closest" more accurately! Why is 9 closer to 10 rather than 11? And I would argue that any number is closest to itself, so 1:8 would be my answer ;)

Answer 1

[KSSV]

Read about knnsearch.

A = [4 9 7 3 10 19 2 11] ;

B = [4 5 2 1 2 8 4 5] ;

idx = knnsearch(A',A','k',2) ;
iwant = idx(:,2)

[Andrei Bobrov]

+1

Answer 2

[Andrei Bobrov]

a = [4 9 7 3 10 19 2 11];

[~,iout] = min(abs(a(:)-a(:)')+diag(nan(numel(a),1)),[],2);

Answer 3

[Roger Stafford]

Let 'a' be your array (row vector.)

n = size(a,2);
[t,p] = sort(a);
q = 1:n; q(p) = q;
t = diff(t);
t = [inf,t;t,inf];
[~,r] = min(t);
r = (1:n)+2*r-3;
p = p(r(q));  % p is the desired result