How to use firs value from array column when threshold and others change to zero, moreover if zero repeated for number of times change that element value?

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Mantas Vaitonis 2018-7-5

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https://ww2.mathworks.cn/matlabcentral/answers/408957-how-to-use-firs-value-from-array-column-when-threshold-and-others-change-to-zero-moreover-if-zero-r

关闭： Mantas Vaitonis 2018-7-5

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Hello Everyone, I have the following code, which was provided by @Stephen Cobeldick, that converts array D

D= -2   2   3  -1  -5
 1   4  7   3   4
 5   3  -4   6  -5
-7  -2   -1   4  -1

To array B.

B=0   2   3   0   0
   1   0  0  3   4
   0   0   0   0  -5
  -7  -2   -1   0   0
   0    2    0   -5  0

Here is the code for that:

   X= D>thr;
Y = D<thr & cumsum(X)>0;
Z = [X(1,:); diff(X)>0 | diff(Y)>0];
 B = zeros(size(D));
 B(Z) = D(Z)

In short this algorithm takes first value when threshold is reached and others are filled with zero. Now I would like to modify B array, that if zeros is repeated two times in a row, it would be change to -1 and the next value which is above or below threshold is changed to zero that result N array would look and the structure should be the same as in original array B that there can not be like this 1 0 0 -1 0 -1, it should be 1 0 0 -1 0 0:

N=0  2  3  0 0
   1  0  0  3 4
   0 -1 -1  0  -5
  -7  0  0  0   0
   0  2  0  -5  0

I have the following code that counts how many time value occurs in a row, but it just a bit of what I need:

x = [4 4 4 1 1 1 5 5 5 0 0 0 7 7 7 1 1 1 1];
i = find(diff(x)) ;
n = [i numel(x)] - [0 i];
c = arrayfun(@(X) X-1:-1:0, n , 'un',0);
d=cellfun(@(x) fliplr(x),c,'un',0);
y = cat(2,c{:});