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

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Ahoora Saadat 2017-3-21

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https://ww2.mathworks.cn/matlabcentral/answers/331023-how-can-i-count-the-number-of-times-the-value-of-an-array-vector-matrix-changes-value-from-x-to-y

评论： Ahoora Saadat 2017-3-22

采纳的回答： Thorsten

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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.

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Answer 1

Thorsten 2017-3-21

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firstvalue = 2;
nextvalue = 1;
A = A(:); % convert matrix to vector
N = nnz(A(1:end - 1) == firstvalue & A(2:end) == nextvalue);

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Ahoora Saadat 2017-3-22

编辑：Ahoora Saadat 2017-3-22

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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