Fixation Overlap Measure — fixation

Calculate the number of overlapping fixations between two fixation groups, based on a minimum distance threshold, and the percentage of overlapping fixations.

Usage

fixation_overlap(
  x,
  y,
  dthresh = 60,
  time_samples = seq(0, max(c(x$onset, y$onset)), by = 20),
  dist_method = c("euclidean", "manhattan")
)

Arguments

x: A `fixation_group` object representing the first fixation group.
y: A `fixation_group` object representing the second fixation group.
dthresh: A numeric value specifying the distance threshold to determine when two fixations overlap (default is 60).
time_samples: A numeric vector of points in time at which to evaluate the overlapping fixations (default is `seq(0, max(c(x$onset, y$onset)), by = 20)`, built from both groups so that the measure is symmetric in `x` and `y`).
dist_method: A character string specifying the distance metric to use for measuring the distance between fixations. Options are "euclidean" and "manhattan" (default is "euclidean").

Value

A list containing the following elements:

overlap: The number of overlapping fixations between the two fixation groups.
perc: The proportion of time points at which both groups have a fixation that overlap (time points before either group's first fixation are not counted).

Details

This function computes the number of overlapping fixations within a minimum distance for two fixation groups at specified time points. An overlap occurs when the distance between two fixations is less than the specified distance threshold.

Examples

# Create two fixation groups
fg1 <- fixation_group(x = runif(50, 0, 100), y = runif(50, 0, 100),
duration = rep(1, 50), onset = seq(1, 50))
fg2 <- fixation_group(x = runif(50, 0, 100), y = runif(50, 0, 100),
duration = rep(1, 50), onset = seq(1, 50))

# Calculate the number of overlapping fixations and the percentage of overlapping fixations
result <- fixation_overlap(fg1, fg2)
overlap <- result$overlap
perc <- result$perc