Sign switching in a sequence

I have a column vector for example,

A=[10; 30; 30; 40; 60; 70; 50; 50; 60; 20; 20]

What I want to do is count each time a number makes a transition from a smaller number to a large number, to count the numbers of times a number makes a transition from a larger number to a smaller number and the number of times the is no change in numbers.

Any help would be great thanks!

Answer 1

[Doug Hull]

Look at the diff command. It will subtract each element from the next. Look at the sign of that calculation and you will be all set.

>> A=[10; 30; 30; 40; 60; 70; 50; 50; 60; 20; 20]

A =

      10
      30
      30
      40
      60
      70
      50
      50
      60
      20
      20

>> d = diff(A)

d =

      20
       0
      10
      20
      10
     -20
       0
      10
     -40
       0

>> nnz(d > 0)

ans =

       5

>> nnz(d < 0)

ans =

       2

>> nnz(d == 0)

ans =

       3

Answer 2

[Azzi Abdelmalek]

ii=histc(sign(diff(A)),[-1;0;1])

%ii(1) correspond to switch high-low
%ii(2)               no switch
%ii(3)               switch low-high

doc diff
doc sign
doc histc

[olig]

Thanks!