The package implements the following methods
Each method has additional parameters that can be passed via the
options argument of the
The algorithm labels a sample as a saccade if velocity, measured in units of its standard deviation (see below), exceeds a predefined threshold (defaults to \(6\)) and the duration of a super-threshold period exceeds a minimal duration (defaults to \(12\) milliseconds). This method makes no assumptions about velocity in the units of degrees per second and can be used on any data (e.g., where samples encode gaze in screen position units).
The standard deviation is computed following formula #2 in Engbert and Kliegl (2003) as
sqrt(median(x^2) - median(x)^2)
However, if the value is smaller than
it is recomputed via a mean estimator
sqrt(mean(x^2) - mean(x)^2)
Only a monocular version of the algorithm is implemented with binocular saccades computed using overlapping votes from two eyes. For method details and rationale for default parameter values refer to Engbert and Kliegl (2003).
ek_velocity_thresholdVelocity threshold for saccade detection in standard deviations. Defaults to \(6\).
ek_sd_funFunction used to compute standard deviation for velocities. Defaults to
sd_via_median_estimator()that implements formula #2 in Engbert and Kliegl (2003). Can be replaced with
mad(), or a custom function.
ek_minimal_duration_msMinimal duration of a saccade in milliseconds. Defaults to \(12\).
ek_minimal_separation_msA minimal required time gap between saccades. Defaults to \(12\).
For method details and rationale for default parameter values refer to Otero-Millan et al. (2014).
om_minimal_inter_peak_time_msMinimal inter-peak interval in milliseconds. Defaults to \(30\)
om_maximal_peaks_per_secondMaximal allowed number of peaks per second. Defaults to \(5\).
om_velocity_threshold_deg_per_secThreshold saccade velocity in °/s. Defaults to \(3\).
om_pca_variance_thresholdMinimal variance explained by retained rotated components. Defaults to \(0.05\).
For method details and rationale for default parameter values refer to Nyström and Holmqvist (2010).
nh_max_velocityMaximal physiologically plausible velocity in °/s. Defaults to
nh_max_accelerationMaximal physiologically plausible acceleration in °/s². Defaults to
nh_initial_velocity_thresholdInitial velocity threshold in °/s. Defaults to