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Counting number of bursts

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How can I count the number of periods of activity above a certain threshold?
I have an EMG signal with some bursts of activity above baseline. I have used the following code to identify those periods of activity (at least 200 points) above a predetermined threshold value that I have chosen:
above_threshold = (EMG_signal > threshold);
spanLocs = bwlabel(above_threshold);
spanLength = regionprops(spanLocs, 'area');
spanLength = [spanLength.Area];
goodSpans = find(spanLength>=200);
allInSpans = find(ismember(spanLocs, goodSpans));
Now I would like to count the number of bursts that have been identified above (i.e. see image attached. In this example, in red are shown the bursts identified).
Any help is much appreciated. Thanks a lot. Antonio

Accepted Answer

Image Analyst
Image Analyst on 9 Aug 2016
Simply call bwareafilt and bwlabel. So get rid of all that and just simply have this:
EMG_signal = [1 2 4 2 0 0 2 2 0 2 0 2 2 2] % Sample signal with 2 bursts
threshold = 1.5
above_threshold = (EMG_signal > threshold)
minAcceptableLength = 3; % or 200 or whatever.
% Find spans that are long enough.
isLongEnough = bwareafilt(above_threshold, [minAcceptableLength, inf])
% Count the number of spans (bursts) that are long enough.
[labeledSpans, numberOfBursts] = bwlabel(isLongEnough)
  4 Comments
Image Analyst
Image Analyst on 16 Jan 2017
Try this:
EMG_signal = [1 1 2 4 2 0 0 2 2 0 2 0 2 2 2 0 4 4 4 4 1] % Sample signal with 2 bursts
threshold = 1.5
above_threshold = (EMG_signal > threshold)
minAcceptableLength = 3; % or 200 or whatever.
% Find spans that are long enough.
isLongEnough = bwareafilt(above_threshold, [minAcceptableLength, inf])
% Specify the max number of zeros 0's there are that should be filled in.
maxHoleSize = 4;
holes = bwareafilt(~isLongEnough, [0, maxHoleSize])
% Don't take any holes if they are on the front or end of the vector
% because they are not bounded by spans on each side.
firstZero = find(holes, 1, 'first')
lastZero = find(holes, 1, 'last')
holes(1:firstZero) = 0;
holes(lastZero:end) = 0
% Now fill in the hoels by ORing:
isLongEnough = isLongEnough | holes;
% Count the number of spans (bursts) that are long enough.
[labeledSpans, numberOfBursts] = bwlabel(isLongEnough)
% Find the lengths of all the spans
props = regionprops(labeledSpans, 'Area');
allLengths = [props.Area]

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