plot_sample_velocity: Plot the sample-to-sample velocity of eye tracking data.

In kollaR: Filtering, Visualization and Analysis of Eye Tracking Data

Plot the sample-to-sample velocity of eye tracking data.

Description

This function visualizes the sample-to-sample velocity in a period of eye tracking data. This can be helpful when determining a suitable velocity threshold for saccade detection Input data must be a data frame with the variables timestamp, x.raw and y.raw as variables. Other variables can be included but will be ignored. This function does not perform pre-processing in the form of interpolation or smoothing. Use the function process.gaze for this. Timestamps are assumed to be in milliseconds. Default settings assume that x and y coordinates are in pixels. The output data is a plot of sample-to-sample velocity in the selected interval.

Usage

plot_sample_velocity(
  data_in,
  velocity.filter.ms = 20,
  plot.window = c(NA, NA),
  xcol = "x.raw",
  ycol = "y.raw",
  threshold.line = NA,
  one_degree = 40,
  verbose = TRUE
)

Arguments

data_in	Data frame with gaze data to plot. Include the variable timestamp with timing in ms and columns with raw x and y data as specified by the paramerers xcol and ycol or their default values
velocity.filter.ms	Window in milliseconds for moving average window used for smoothing the sample-to-sample velocity vector.
plot.window	vector defining the time window to plot. If left empty, the 50-65 <0, they are assumed to be proportions, e.g., plot.window = c(0.3,0.35) plots the 30-35 percent of max.length interval of the data. Numbers >1 are assumed to refer to sample order in the data
xcol	Name of the column where raw x values are stored. Default: "x.raw"
ycol	Name of the column where raw y values are stored. Default: "y.raw"
threshold.line	Can be specified to add a line showing a potential velocity threshold for saccade detection. No threshold is shown if this parameter is NA
one_degree	One degree of the visual field in the unit of the raw x and y coordinates, typically pixels
verbose	If TRUE, print the resulting plot

Value

A ggplot showing the sample-to-sample velocity of the selected data interval

Examples

plot_sample_velocity(data_in = sample.data.processed, threshold.line = 35)

kollaR documentation built on April 13, 2025, 5:11 p.m.