How to take the X smaller values of an array ?

Hello everyone,

I have an array x (for example size(x)= 1, 10) and x=(1, 4, 100, 3, 14, 56, 8, 90, 23, 2).

My question is how can I keep the 6 smaller values of x without making a sort ? Because when I do a sort, it changes the place of the values.

For example if y is the output array I want that y=(1, 4, 3, 14, 8, 2)

Thanks for reading.

Answer 1

[Adam]

[y,idx] = sort( x );
[~,idx2] = sort( idx(1:6) );
y = y( idx2 );

There may be a slightly more elegant way, but that does the job.

[Hidir ABAY]

Thank you very much I exactly understand what you said.

Answer 2

[Paxorus Sahay]

This sliding insertion technique might be what you're looking for.

function [minima] = smallest(vec, n)
    minima = vec(1:n);
    [maxElem, idx] = findMax(minima);
    for i = (n+1):length(vec)
        if vec(i) < maxElem
            minima(idx:end) = [minima(idx+1:end) vec(i)];
            [maxElem, idx] = findMax(minima);
        end
    end
end

function [maxElem, firstIndex] = findMax(vec)
    % assuming vec not empty
    maxElem = max(vec);
    allMatches = find(vec == max(vec));
    firstIndex = allMatches(1);
end

Example usage:

x = [1, 4, 100, 3, 14, 56, 8, 90, 23, 2];
y = smallest(x, 6);