Data Files
©
2016-2017 SR Research Ltd.
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All events and samples appear in temporal order. That is, the timestamps of
samples, end-time timestamps of eye-movement end events, and start-time
timestamps of all other events will be the same or greater than any preceding
data.
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Eye-data samples are nested between eye-movement start and end events.
For example, the first sample in a fixation will follow the SFIX event for that
fixation, and the EFIX event for a fixation will follow the last sample in the
fixation. This allows on-the-fly classification of samples as the data file is
read.
Before writing an analysis program to process an ASC file, it is helpful to
convert a small EDF file containing the data of interest, and examine it with a
word processor or print it out.
4.9.2 Sample Line Format
Sample lines contain time, position, and pupil size data. Optionally, velocity
and resolution data may be included. Each sample line begins with a
timestamp. Recordings done with a 2000 Hz sampling rate will have two
consecutive rows with the same time stamps. The second row refers to the
sample collected at 0.5 ms after the reported time stamp. (To avoid identical
time stamps in a 2000 Hz recording file, you may consider adding the -ftime
switch if you do the file conversion from the command prompt, or enable the
“Output Float Sample” option in the GUI version of the EDF2ASC converter.)
The time stamp field is followed by X and Y position pairs and pupil size data
for the tracked eye, and optionally by X and Y velocity pairs for the eye, and
resolution X and Y values. Missing data values are represented by a dot ("."), or
the text specified by the "-miss" option to EDF2ASC.
Several possible sample line formats are possible. These are listed below.
SAMPLE LINE FORMATS
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Monocular:
<time> <xp> <yp> <ps>
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Monocular, with velocity
<time> <xp> <yp> <ps> <xv> <yv>
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Monocular, with resolution
<time> <xp> <yp> <ps> <xr> <yr>
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Monocular, with velocity and resolution
<time> <xp> <yp> <ps> <xv> <yv> <xr> <yr>
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Binocular
<time> <xpl> <ypl> <psl> <xpr> <ypr> <psr>
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Binocular, with velocity
<time> <xpl> <ypl> <psl> <xpr> <ypr> <psr> <xvl> <yvl> <xvr> <yvr>