index_max_velocity {mousetRajectory}

Time point of maximum velocity

Description

Computes the index of the peak velocity of a trajectory, defined by vectors of x and y coordinates, and assumed to be equidistant in time.

Usage

index_max_velocity(x_vector, y_vector)

Arguments

x_vector

x-coordinates of the executed path.

y_vector

y-coordinates of the executed path.

Details

The supplied vectors are assumed to be ordered by time with equal time differences.

Value

Single number indicating the index of peak velocity (1 to +Inf).

References

Wirth, R., Foerster, A., Kunde, W., & Pfister, R. (2020). Design choices: Empirical recommendations for designing two-dimensional finger tracking experiments. Behavior Research Methods, 52, 2394 - 2416. doi:10.3758/s13428-020-01409-0

Examples

x_vals <- c(0, 1, 2, 3, 6, 10, 12, 14, 15)
y_vals <- c(0, 0, 0, 0, 0, 0, 0, 0, 0)
index_max_velocity(x_vals, y_vals)
# velocity maximal between x_vals[5] and x_vals[6]

numbers <- seq(-(3 / 4) * pi, (3 / 4) * pi, by = 0.001)
y_vector <- sin(numbers)
plot(numbers, y_vector)
index_max_velocity(rep(0, length(numbers)), y_vector)
abline(v = numbers[index_max_velocity(rep(0, length(numbers)), y_vector)])
which.max(cos(numbers)) # first derivative of sin, max at 0 degrees