MATLAB: Checking if an array element is larger than the following elements

array

So if I have a large array of form A=[1,5,6,4,12…], is there a consistent way of checking if some element A(n), let's say A(3), is larger than the following ones? So in this case, I would like to find out that A(3)>A(4). Also, then I would like to change those elements in a way that any element A(n) is always equal or larger than any of the elements before it. So again, in this case I would like to change my array A from [1,5,6,4,12…] -> [1,4,4,4,12…] or [1, NaN, NaN,4,12,…].
Thank you.

Best Answer

This is not hard. Please feel encouraged to try it by your onw.
A = [1,5,6,4,12];
X = A(length(A));
for k = length(A)-1:-1:1
  if A(k) > X
    A(k) = X;  % Or: NaN
  else
    X = A(k);
  end
end
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