R package to import eye tracking recording generated by SR Research EyeLink eye tracker from EDF-files. It includes options to import events and/or recorded samples and extract individual events such as saccades, fixations, blinks, and recorded variables.
These instructions are also available as a vignette.
The library installation involves three easy (famous last words) steps.
This package relies on edfapi library that is as part of the
EyeLink Developers Kit. Therefore, read_edf()
function will not work without it but you will still be
able to use utility functions. The EyeLink Developers Kit can
be downloaded from sr-support.com website. Note that
you need to register and wait for your account to be activated. Next,
follow instructions to install EyeLink Developers Kit for your
platform. The forum thread should be under SR Support Forum ›
Downloads › EyeLink Developers Kit / API › Download: EyeLink Developers
Kit / API Downloads (Windows, macOS, Linux).
The package needs to configure compiler flags for its dependency on EDF API library. Specifically, it needs to specify paths to include header files ( edf.h, edf_data.h, and edftypes.h) and to the library itself. The package will try to compile using sensible defaults for each platform, i.e., default installation paths for EyeLink Developers Kit v2.1.1. However, these defaults may change in the future or you may wish to install the library to a non-standard location (relevant primarily for Windows).
If compilation with default paths fails, you need to define R
environment variables as described below. These variables must be
defined either in user or project .Renviron
file. The simplest way to edit it is via usethis library and edit_r_environ()
function. Type usethis::edit_r_environ() for user and
usethis::edit_r_environ('project') for projects
environments (note that the latter shadows the former, read documentation for details). Note
that in the case of Windows, you do not need to worry about forward
vs. backward slashes as R will normalize strings for you. Once you
define the variables, restart session and check them by typing
Sys.getenv() (to see all variables) or
Sys.getenv("EDFAPI_INC") to check a specific one.
Default values assume that the EyeLink Developers Kit is installed in
c:/Program Files (x86)/SR Research/EyeLink (default
installation path).
EDFAPI_LIB : path to edfapi.dll for
32-bit systems. Defaults to
c:/Program Files (x86)/SR Research/EyeLink/libs.EDFAPI_LIB64 (optional): path to
edfapi64.dll for 64-bit systems. By
default, the 64-bit library is in x64 subfolder, i.e.,
c:/Program Files (x86)/SR Research/EyeLink/libs/x64. This
variable is optional, as the package will try to guess this by itself by
appending /x64 to EDFAPI_LIB path. However,
you should specify this variable explicitly if 64-libraries are in a
non-standard folder (or SR Research changed it, or you just want to be
sure).EDFAPI_INC : path to C header files necessary for
compilation. Specifically, the package requires edf.h,
edf_data.h, and edftypes.h. Defaults to
c:/Program Files (x86)/SR Research/EyeLink/Includes/eyelink.Your .Renviron file include lines similar to the ones
below
EDFAPI_LIB="c:/Program Files (x86)/SR Research/EyeLink/libs"
EDFAPI_LIB64="c:/Program Files (x86)/SR Research/EyeLink/libs/x64"
EDFAPI_INC="c:/Program Files (x86)/SR Research/EyeLink/Includes/eyelink"EDFAPI_INC : path to C header files necessary for
compilation. Specifically, the package requires edf.h,
edf_data.h, and edftypes.h. Defaults to
/usr/include/EyeLink.Your .Renviron file should include a line like this
EDFAPI_INC="/usr/include/EyeLink"EDFAPI_LIB: path to EDF API framework. Defaults to
/Library/FrameworksEDFAPI_INC : path to C header files necessary for
compilation. Specifically, the package requires edf.h,
edf_data.h, and edftypes.h. Defaults to
/Library/Frameworks/edfapi.framework/HeadersYour .Renviron file include lines similar to the ones
below
EDFAPI_LIB="/Library/Frameworks"
EDFAPI_INC="/Library/Frameworks/edfapi.framework/Headers"To install from github
library("devtools")
install_github("alexander-pastukhov/eyelinkReader", dependencies=TRUE)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)There is a basic utility for plotting saccades and fixations for an individual trial
plot(gaze, trial = 1, show_fixations = TRUE, show_saccades = TRUE)or across trials
plot(gaze, trial = NULL, show_fixations = TRUE, show_saccades = FALSE)The package also includes functions to parse non-standard events:
recorded areas of interest (extract_AOIs) and trigger
events that help to time events (extract_triggers). These
need to be called separately.
gaze <- extract_AOIs(gaze)
gaze <- extract_triggers(gaze)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'))See also a vignette on package usage. Please refer to documentation
on eyelinkRecording class for details on events and
samples.
I have attempted to document the package as thoroughly as I could. However, for any question about specific attributes please refer to the EDF API manual and EyeLink documentation, which is supplied by SR Research alongside the library.