# Identify the duration of zero values and count the number of such zero regions

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Reji G on 1 Dec 2022
Commented: Image Analyst on 1 Dec 2022
Hello,
I have a signal shown above.
1. First I want to identify the duration(length) of each zero valued regions represented as T, T1, T2, T3 etc., (You may generate any signal with zeroed region similar to my graph)
2. Count how many such zero valued regions are there in 1 sec(or within a specified time).
Any help interms of code is well appreciated. Thank you in advance.

Davide Masiello on 1 Dec 2022
Edited: Davide Masiello on 1 Dec 2022
time = 0:100;
signal = rand(size(time));
signal([3:6,15:21,43:55,61:64,87:92]) = 0;
plot(time,signal)
r = regionprops(signal==0,"SubarrayIdx");
for k = 1:length(r)
time_indexes = r(k).SubarrayIdx{2};
durations(k) = time(time_indexes(end))-time(time_indexes(1));
end
durations
durations = 1×5
3 6 12 3 5
Obviously, the number of zero regions is the length of the array durations.
Image Analyst on 1 Dec 2022
Or, more simply
zeroRegions = (signal == 0); % Identify elements that are exactly 0.
% Throw out runs less than, say, 3 elements long.
zeroRegions = bwareaopen(zeroRegions, 3);
% Measure what's left (regions 3 or more elements long).
r = regionprops(zeroRegions,"Area");
durations = [r.Area] % Extract all run lengths from structure into vector.

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