maxk from subset of array

Hi,

I would like to solve the following prblem:

Lets say i have the vector :v=[10,22,3,-5,8,6,100,30,12,9]

I want to find the indicies and the values of the k largest number from a given subset, e.g: if the indices of the subset are [1,3,5,8] and k=2 the function will return: values=[10,30], indices=[1,8].

There is any suggestion how to implemet it?

Thanks

Answer 1

[Yazan]

clc, clear 

v = [10,22,3,-5,8,6,100,30,12,9];
subIdx = [1,3,5,8];
k = 2;

% sort values and get corresponding indices
[val, idx] = sort(v(subIdx), 'descend');
% get only k values
val = val(1:k);
% get actual indices
Idx = subIdx(idx(1:k));

val

val = 1×2

30 10

Idx

Idx = 1×2

8 1

[Orr Streicher]

thanks!

[Yazan]

You may also use Matlab native function maxk instead of sorting the values. This might save you some processing power.