How can I count the number of times the value of an array/vector/matrix changes value from x to y?

For example

 Let A = [1;2;1;1;1;3;5;5;5;1;1;1;6;3;4;2;8;6;6;6;6]

How can I determine the number of times the value goes from say 2 to 1, or from 6 to 3 or from 1 to 1 etc. ?

Thank you.

Answer 1

[Thorsten]

firstvalue = 2;
nextvalue = 1;
A = A(:); % convert matrix to vector

N = nnz(A(1:end - 1) == firstvalue & A(2:end) == nextvalue);

[Ahoora Saadat]

Thank you!!!

[Ahoora Saadat]

So if I wanted this to be done for an n row column vector with possible values going from 1 to m then would the following work:

 for i = 1:1:m
     fv = i;
     for j = 1:1:m
         nv = j;
         a_i = sum(SA(:) == i) ; % This is the number of times that the system is in state s = i
         b_i_j = nnz(SA(1:end - 1) == fv & SA(2:end) == nv); % Where b_i_j is the number of times the system goes from state s = i to state s = j
         T_1(i,j) = b_i_j/a_i ; % Where T_1 is the m-by-m transition matrix.
     end
 end

Thank you again.

[Ahoora Saadat]

Never mind it worked!!! Thank you so much!