KTHVALUE (v2.1, jun 2012)

select the k-th smallest element in a (randomized) list
Updated 2 Jul 2012

View License

KTHVALUE - select the k-th smallest element in a (randomized) list

V = KTHVALUE(L,K) returns the K-th smallest number from a list. L is
(unordered) list of N values, and K is a scalar between 1 and N.

L = ceil(10*rand(1,6)), K = 3
V = kthvalue(L,K)

The result is equivalent to picking the K-th value in the sorted list
"sort(L)". However, KTHVALUE does not require the explicit creation of
a temporary array, and is often faster.

L = rand(10000,1000) ; K = ceil(numel(L)/2) ;
tic ; V1 = kthvalue(L,K) ; toc
% Elapsed time is 0.73 seconds. (on average)
tic ; B = sort(L(:)) ; V2 = B(K) ; toc ;
% Elapsed time is 1.79 seconds.
isequal(V1,V2) % of course ...

- Despite its nice algorithm, I would recommend the approach using SORT
over KTHVALUE, primarily because with one call to SORT one can
extract multiple elements.
- To find the k-th largest element, use -KTHVALUE(-L,K)
- For lists L with (2*K-1) numbers, KTHVALUE(L,K) equals the median
value of L.
- KTHVALUE can be used as a (rather inefficient ;-) ) sorting algorithm:
A = rand(5,1) ;
sortedA = zeros(size(A)) ;
for i=1:numel(A),
sortedA(i) = kthvalue(A,i) ;
[sort(A) sortedA]

For some more ideas on element selection see

See also sort, min, max, median

Cite As

Jos (10584) (2024). KTHVALUE (v2.1, jun 2012) (https://www.mathworks.com/matlabcentral/fileexchange/23195-kthvalue-v2-1-jun-2012), MATLAB Central File Exchange. Retrieved .

MATLAB Release Compatibility
Created with R13
Compatible with any release
Platform Compatibility
Windows macOS Linux
Find more on Shifting and Sorting Matrices in Help Center and MATLAB Answers

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!
Version Published Release Notes

fixed warning issue about for-loop that popped up in newer releases of matlab