The log of the (speed-based) dimensionless jerk, negated so that more negative = less smooth.
Examples
t <- seq(0, 1, length.out = 200); tau <- t
speed <- 30 * tau^2 - 60 * tau^3 + 30 * tau^4
ldlj(speed, fs = 200)
#> [1] -5.311984
The log of the (speed-based) dimensionless jerk, negated so that more negative = less smooth.
t <- seq(0, 1, length.out = 200); tau <- t
speed <- 30 * tau^2 - 60 * tau^3 + 30 * tau^4
ldlj(speed, fs = 200)
#> [1] -5.311984