Checking if an array element is larger than the following elements

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.

[Jan]

What have you tried so far? This can be solved with a loop.

[Valtteri Tikkanen]

I have tried this:

A=[1,5,6,4,12,14,13];

for i=2:7
if gt(A(i-1),A(i))
        A(i-1)=A(i)
    end
end

Which produces A=[1,5,4,4,12,13,13]. The problem is that I do not know how reach elements further away, so for example A(2) is not corrected.

[Stephen23]

Try this:

A = [1,5,6,4,12];
for k = numel(A)-1:-1:1
    A(k) = min(A(k:k+1));
end

Answer 1

[Jan]

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

[Valtteri Tikkanen]

Thank you very much, this solved my problem!