Usage"
In eyelinkReader: Import Gaze Data for EyeLink Eye Tracker

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)

library(eyelinkReader)

The main function is read_edf() that imports an EDF file (or throws an error, if EDF API is not installed). By default it will import all events and attempt to extract standard events: saccades, blinks, fixations, logged variables, etc.

library(eyelinkReader)
gaze <- read_edf('eyelink-recording.edf')

Events and individual event types are stored as tables inside the eyelinkRecording object with trial column identifying individual trials. Trial 0 correspond to events (e.g, DISPLAY_COORDS message, etc.) sent to the eye tracker before the first trial.

View(gaze$saccades)

Working with samples

To import samples, add import_samples = TRUE and, optionally, specify which sample attributes need to be imported, e.g., sample_attributes = c('time', 'gx', 'gy'). All attributes are imported if sample_attributes is not specified. See package and EDF API documentation for the full list of attribute names.

# import samples with all attributes
gaze <- read_edf('eyelink-recording.edf', import_samples = TRUE)

# import samples with selected attributes
gaze <- read_edf('eyelink-recording.edf',
                 import_samples = TRUE,
                 sample_attributes = c('time', 'gx', 'gy'))

You can convert makes samples cyclopean. In case of a binocular recording, a single column would represent an average between to eyes. E.g., $gx = (gxL + gxR) / 2$. In case of a monocular recording, a single column will contain information for a recorded eye. This is particularly useful, if you have multiple monocular recordings but some for the right eye and some for the left.

cyclopean_samples <- compute_cyclopean_samples(gaze$samples)

Utility functions

The package includes various utility functions that need to be called separately. For example, to parse non-standard events: recorded areas of interest (extract_AOIs) and trigger events that help to time events (extract_triggers).

gaze <- extract_AOIs(gaze)
gaze <- extract_triggers(gaze)

or, tidyverse-style

library(tidyverse)
gaze <-
  read_edf('eyelink-recording.edf') %>%
  extract_AOIs() %>%
  extract_triggers()

Function adjust_message_time() alters time stamps of messages that are prefixed by a numeric offset that makes synchronization easier for e E-Prime / Presentation. I.e., a message "-50 TARGET_ONSET" that was sent at 105600 becomes a message "TARGET_ONSET" and its time stamp is 105550.