How can I compare vector`s values?

I have a vector like on the figure bellow. I extracted the min and max values of it (A,B,C,D,E,F,G) and now I need to make a comparison of all the consecutive values and put the difference in another vector. In other words to find the difference between the values A with B; B with C etc. (named 1,2,3,4,5,6 on the figure).

And my code:

b=[1 2 3 4 5 6 7 8 9 8 7 6 5 4 5 6 7 8 9 10 7 4 3 2 1 4 7 8 9 7 6 5 4 3 4 5 6 7 8 3 2 1];
k=numel(b);
MIN=zeros(1,k);
MAX=zeros(1,k);

 for i=3:k
 if b(i-1)>b(i-2) && b(i-1)>b(i)
 MAX(i-1)=b(i-1);
 end
 end

 for i=3:k
 if b(i-1)<b(i-2) && b(i-1)<b(i)
 MIN(i-1)=b(i-1);
 end
 end

MIN=MIN(MIN~=0);
MAX=MAX(MAX~=0);

Answer 1

[Thorsten]

Index of extrema:

   b = b(:);
   idx = find(([b(1); b(1:end-1)] - b).*([b(2:end); b(end)] - b) > 0);

Difference between extrema

   d = diff(b(idx));

[Miro Mitev]

It gives me this (for the index of extrema):

Error using vertcat

Dimensions of matrices being concatenated are not consistent.

[Thorsten]

I added b = b(:) to convert b to a column vector.

[Miro Mitev]

Thank you! It is exactly what i was searching for.