Segmenting Data around an event

I am trying to segment data to epoch it around an active event, but keep having issues. Currently I am finding every index where states.Active is true, but this ends up giving me segments that are one sample off from each other. I want to segment the data by finding the indices where state.Active changes from 0 to 1 so the rising edge. Below is what I have. Thank you for your time!

%segment data

fs = 240;

sampleDuration = 0.8;

numSamplesToCollect = round(sampleDuration * fs);

% Identify flashing

flashingIndices = find(state.Active == 1);

% Store collected segments

collectedSegments = cell(length(flashingIndices), 1);

% Segment data per channel per fs around flash

for i = 1:length(flashingIndices)

% Get the index of the flash

flashIndex = flashingIndices(i);

% Define start and end indices for segment

startIdx = flashIndex - round(numSamplesToCollect / 2);

endIdx = flashIndex + round(numSamplesToCollect / 2) - 1; % -1 to include the endpoint

% Ensure indices are within bounds

if startIdx < 1

startIdx = 1; % Avoid negative index

end

if endIdx > length(signal)

endIdx = length(signal); % Avoid exceeding signal length

end

% Collect the segment

collectedSegments{i} = signal(startIdx:endIdx);

end

% Check the result

disp(collectedSegments);

[Image Analyst]

I'd have to debug it, since I can't do it just by looking at your code. But you didn't attach any data.

If you have any more questions, then attach your data and code to read it in with the paperclip icon after you read this:

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Answer 1

[Voss]

Active = [1 0 0 1 1 1 0 0 1]

Active = 1×9

1 0 0 1 1 1 0 0 1

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flashIndex = strfind(Active,[0 1])+1 % index of the 1 at the rising edge

flashIndex = 1×2

4 9

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If you want to consider a 1 that starts the signal to be a "rising edge":

flashIndex = strfind([0 Active],[0 1]) % index of the 1 at the rising edge

flashIndex = 1×3

1 4 9

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