Are there any functions to randomly pick the minimum element from a vector if the vector has multiple minimum elements?

Function min() picks the first minimum element from a vector if the vector has multiple minimum elements.

I want to randomly pick the minimum element from all the minimum elements and get its value and index.

Could you tell me if there is a function to do that?

Answer 1

[Walter Roberson]

No, there is no function provided for that. You can write such a function, though. The difficulty of doing it will depend upon whether you are working with a vector or something that is at least 2D (in which case it has to process per row or per column)

[Walter Roberson]

For the scalar case:

minval = min(TheVector);
idx = find(TheVector == minval);
idx = idx(randi(length(idx)));

[Ryan]

The code is great and illuminating!

Actually, I want to randomly pick the minimum element consecutively three times as follows.

Step 1, I randomly pick the minimum element among all the minimum elements and get its value and index.

Step 2, I exclude the element picked in Step 1 and randomly pick the minimum element among all the minimum elements and get its value and index.

Step 3, I exclude the elements picked in Step 1 and Step 2 and randomly pick the minimum element among all the minimum elements and get its value and index.

Could you further help me?

[Walter Roberson]

That sounds like homework.

I will give a hint: if you set a value to nan then it will no longer be a minimum (unless everything is nan.)

[Ryan]

Thanks a lot!

Actually, I though of setting the value as Inf. But I am afraid the program will have bugs during the later programming. Seriously...

It is not homework. Seriously...

Anyway, thanks a lot!

[Walter Roberson]

NR = 3;
[sortedvals, sortidx] = sort(YourVector);
LastSameIdx = 1;
MinVals = zeros(1,NR);
RandomIdx = zeros(1,NR);

for K = 1 : NR
    LastSameIdx = 1;
    while LastSameIdx < length(YourVector) && sortedvals(1) == sortedvals(LastSameIdx+1)
      LastSameIdx = LastSameIdx + 1;
    end
    thisidx = randi(LastSameIdx);
    MinVals(K) = sortedvals(thisidx);
    RandomIdx(K) = sortidx(thisidx);
   sortedvals(thisidx) = [];
   sortidx(thisidx) = [];
end

Outputs are MinVals and RandomIdx.