Per-step speed along a trajectory

Speed of each step as straight-line step distance divided by the elapsed time of that step: `sqrt(diff(x)^2 + diff(y)^2) / diff(seconds)`. The unit is the distance unit of `x`/`y` per second; for radiatR's unit-circle coordinates that is radii per second.

Usage

step_speed(x, y, seconds)

Arguments

x, y

Numeric vectors of ordered (in time) coordinates for one trajectory.

seconds

Numeric vector, the elapsed time of each point in seconds (same length as `x`/`y`).

Value

A numeric vector of per-step speeds, length `length(x) - 1`. A step is `NA` when either endpoint is non-finite or its time increment is `<= 0`; `numeric(0)` when fewer than two points are given.

See also

[track_speed()] for a whole `Tracks`; [elapsed_seconds()].

Examples

step_speed(x = 0:3, y = rep(0, 4), seconds = (0:3) / 30)   # 30 units/s
#> [1] 30 30 30