Summarises each trajectory's speed (distance per second). Step speeds come
from [step_speed()] using the track's elapsed time from [elapsed_seconds()];
the per-track summary is the chosen `stat` of those step speeds.
Usage
track_speed(
ts,
stat = c("mean", "max", "median"),
x_col = ts@cols$x,
y_col = ts@cols$y
)
Arguments
- ts
A `Tracks`.
- stat
Per-track reduction of the step speeds: `"mean"` (default),
`"max"`, or `"median"`.
- 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 a
numeric `speed` column (`NA` for tracks with fewer than two usable points).
Details
Numeric (frame) time requires a frame rate ([set_frame_rate()]); POSIXct time
is used directly. With the default coordinate columns the unit is radii
per second, because radiatR normalises trajectories to a unit circle.
See also
[step_speed()], [elapsed_seconds()], [track_duration()],
[straightness_index()]
