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Per-observation angular (turning-rate) velocity for a Tracks

Source: R/track_metrics.R
angular_velocity.Rd

The signed rate of change of travel direction at each point – how fast, and which way, the trajectory is turning. Positive is counter-clockwise (a left turn). Each interior point's turn (the angle between its incoming and outgoing step) is divided by the centred time step; the first and last point of every trajectory are `NA`.

Usage

angular_velocity(
  ts,
  units = c("radians", "degrees"),
  x_col = ts@cols$x,
  y_col = ts@cols$y
)

Arguments

ts

A `Tracks`.

units

`"radians"` per second (default) or `"degrees"` per second.

x_col, y_col

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

Value

A numeric vector, one value per observation in `ts@data` order, `NA` at each trajectory's first and last point.

Details

Numeric (frame) time requires a frame rate ([set_frame_rate()]); POSIXct time is used directly. The result is scale-free (an angle), so no distance calibration is applied.

See also

[velocity_vector()], [instantaneous_speed()], [frame_rate()]

Examples

summary(angular_velocity(cpunctatus, units = "degrees"))
#>    Min. 1st Qu.  Median    Mean 3rd Qu.    Max.     NAs 
#> -36.000   0.000   0.000   1.131   0.636  36.000     470