# Count conservative occurrences of zeros and if zero appeared for defined number of times it should be changed.

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Mantas Vaitonis on 8 Jul 2018
Commented: Mantas Vaitonis on 9 Jul 2018
Hello,
There is an array A size (NxM), each column represents when a signal was created. I need to close that signal if certain time it was not created again and assign -1 value. For example like this:
1 0 1 0 1
0 1 0 1 0
0 0 1 0 0
1 0 0 1 1
0 0 1 1 0
0 1 0 0 0
I need to count consecutive occurrences of zero column-vise, and if zero occurred for defined number of times for example two, it should be changed to -1 and output should look like this:
1 0 1 0 1
0 1 0 1 0
-1 0 1 0 -1
1 -1 0 1 1
0 0 1 1 0
-1 1 0 0 -1
Count conservative occurrences of zeros and if zero appeared for defined number of times it should be changed.
Jan on 8 Jul 2018
I assume you mean "consecutive" instead of "conservative". What is the wanted output for:
x1 = [0; 0; 1]
x2 = [1; 0; 0; 0; 0]

Jan on 8 Jul 2018
Edited: Jan on 8 Jul 2018
If you want to replace the 2nd element after a 1 by -1, if it was a 0 before:
A = double(rand(10, 5) < 0.3); % Some test data
n = 2;
pattern = [1, zeros(1, n)];
for k = 1:size(A, 2)
index = strfind(A(:, k).', pattern);
A(index + n, k) = -1;
end
Mantas Vaitonis on 9 Jul 2018
@Jan, I am using WIN 10 64BIT, yes it would be possible to use UNIT8 instead of double, becasue this varibale valeus are 1, 0 or -1.