labkit.biosignal.segmentByEvents

Description

Extracts one fixed-length signal segment around each event index. Events whose requested window would extend beyond the signal are omitted rather than padded. The returned columns therefore correspond only to interior events, and eventIndex and eventTime identify which events were retained.

Window boundaries are converted to sample counts by rounding after multiplication by signal.fs. The default window is 0.35 seconds before through 0.35 seconds after each event.

Inputs

signal

Biosignal structure with values, fs, and displayName fields.

events

Event structure returned by labkit.biosignal.detectEcgPeaks. index contains 1-based sample positions and time contains the corresponding event times.

windowSec

Optional two-element vector [startSec endSec] relative to an event. Use a negative start and nonnegative end to span the event. The default is [-0.35 0.35] seconds.

Outputs

segments

Structure containing the retained waveform segments.

Output Fields

type

String scalar "biosignalSegments".

values

M-by-N matrix with one retained event segment per column.

timeOffset

M-by-1 vector of sample times relative to the event.

eventIndex

N-by-1 source sample indices of retained events.

eventTime

N-by-1 source times of retained events.

fs

Sample rate in hertz copied from signal.

sourceName

signal.displayName.

metadata.windowSec

Requested window in seconds.

Errors

labkit:biosignal:InvalidSignal

signal lacks values or fs.

labkit:biosignal:InvalidEvents

events lacks index or time.

labkit:biosignal:InvalidWindow

windowSec is not an increasing two-element vector.

Example

signal = struct('values', (1:21)', 'fs', 10, 'displayName', "ECG");
events = struct('index', [6; 16], 'time', [0.5; 1.5]);
segments = labkit.biosignal.segmentByEvents(signal, events, [-0.2 0.2]);