velocity: Compute distribution parameters for velocity
In moveBB: Analysis of Trajectory Data using Linear or Brownian Motion Model

Description Usage Arguments Details Value See Also Examples

The velocity over any time interval is a bivariate normal distribution. This function computes the parameters for this distribution. The velocity in the linear model is identical to the mean velocity, so ignore the variance in that case.

1	velocity(tr, time, time.scale = NA)

`tr`	The trajectory object
`time`	Vector of times
`time.scale`	The length of the intervals over which to report the direction

The velocity at a time t is defined as the net rate of displacement over the time interval [t-time.scale/2, t+time.scale/2], i.e.

v(t, Δ t) = (x(t + Δ t / 2) - x(t - Δ t / 2)) / Δ t.

Returns a three dimensional array indexed by ID in the trajectory, variable name and time. The variables are named x, y and var for the x and y components of the mean and the variance respectively.

bbtraj

data("vervet_monkeys", package="moveBB")

## Compute the velocity distribution parameters over two half-hour intervals
#velocity(monkey.tr, as.POSIXct(c("2011-01-18 15:15:15", "2011-01-19 16:30:00")), 1800)