Sign switching in a sequence

Question

olig 2013-6-7

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/78398-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!

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Answer 1

Doug Hull 2013-6-7

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/78398-sign-switching-in-a-sequence#answer_88102

在 MATLAB Online 中打开

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

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Answer 2

Azzi Abdelmalek 2013-6-7

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/78398-sign-switching-in-a-sequence#answer_88105

编辑：Azzi Abdelmalek 2013-6-7

在 MATLAB Online 中打开

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