i want to find maximum and minimum values in a matrix continuosly

i want to find maximum and minimum values in a matrix

suppose i have data like

1

2

5

6

3

2

5

8

9

1

so my minimum is 1 and maximum is 6 and next minimum is 2 maximum is 9 again 1 like that

i want result as

1

6

2

9

1

Answer 1

[Chien-Han Su]

Try this

% define an arbitray array a 
a = [1, 2, 5, 6, 3, 2, 5, 8, 9, 1];

if length(a) <= 2
    extreme = a;
else
    extreme = zeros(1,length(a));
    extreme(1) = a(1); % first element must be extreme value 
    count = 1; % count the number of extreme value 
    if a(2) > a(1) 
        increase = true; % use 'increase' to record the trend of increasing or decreasing 
    else 
        increase = false;
    end 
    for n = 3:length(a)
        if a(n) > a(n - 1)
            if increase == false
                count = count + 1;
                extreme(count) = a(n - 1);
            end 
            increase = true;
        else
            if increase == true 
                count = count + 1;
                extreme(count) = a(n - 1);
            end 
            increase = false;
        end 
    end 
    extreme(count + 1) = a(end); % last elements must be extreme value 
    extreme = extreme(1:count + 1);
end