Per-trajectory net velocity for a Tracks

The net (average) velocity vector of each trajectory: its straight-line displacement divided by its elapsed duration. The magnitude is the net speed and `atan2(vy, vx)` the overall direction of travel (so a path returning to its start has zero net velocity). Distance-calibrated when a scale is set.

Usage

track_velocity(ts, x_col = ts@cols$x, y_col = ts@cols$y)

Arguments

ts

A `Tracks`.

x_col, y_col

Names of the coordinate columns. Default to the `Tracks`'s recorded x/y columns.

Value

A `data.frame` with one row per trajectory: the id column and numeric `vx`, `vy` (`NA` for tracks with fewer than two points or zero duration).

Details

Numeric (frame) time requires a frame rate ([set_frame_rate()]); POSIXct time is used directly.

See also

[velocity_vector()], [track_speed()], [track_turning()], [set_distance_scale()]