EyeLink II User Manual version 2.12
(07/02/2006)
©
2002-2006 SR Research Ltd.
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4.8.2.3 Sample and Event Selection
The size and readability of the translated ASC file is controlled by selecting the
types of events or samples present. The presence of samples increases file size
by a factor of 10 or 20, compared to events alone. Eliminating all samples and
eye-movement events makes the basic structure of the data file apparent, aiding
design of analysis software.
By default, both samples and events are translated into the output ASC file.
Samples may be eliminated with the "-e" (events only) or "-ns" (no samples)
options. All events may be eliminated with the "-s" (samples only) or "-ne" (no
events) options. This results in a file containing only sample data lines, with no
events, comments, or file structure lines.
More selective event filtering is possible. With the "-nse" (no start events)
option, only summary events (end of fixations, saccades, or blinks) are reported,
which halves the number of eye-movement events and may be acceptable for
hand analysis or simple cognitive experiments. All eye-movement events may
be removed with the "-neye" (no eye) option, resulting in a listing of file
messages and data blocks. This is useful as a summary of file structure when
designing analysis software for experiments. Finally, message events can also
be removed with the "-nmsg" (no messages) option.
Examples of the most useful sets of sample and event selection options are:
edf2asc -ns
no samples, just events
edf2asc -neye
just samples, messages, button events, and data block
events
edf2asc -ne
nothing but sample data
edf2asc -ns -neye file structure outline: messages, buttons, data block
events
Add to these options any sample-data selectors, and eye (-l, -r) data selectors
required.
4.8.2.4 Special Data Options
The formatting of numerical data as text requires the use of a special symbol or
value to indicate missing or undefined data. For example, eye position data is
missing during a blink, as no pupil is present. In some EDF files, required
velocity or resolution data is missing.
By default, such missing data is replaced with a dot ".". Any string or value can
be used to replace the missing data. This value is specified with the "-miss"
option, which is followed by the value to be used. One possibility is to use a
very small value, such as "1e-8".
Resolution data is not available in some EDF files, or for raw pupil-position
data. A default resolution value can be set using the "-defres" option, which is
