TrajDirectionalChange {trajr}

Directional change (DC)

Description

Calculates the time variation of directional change (DC) of a trajectory sensu Kitamura & Imafuku (2015). Directional change is defined as the angular change (in degrees) between two steps in the trajectory, divided by the time difference between the two steps.

Usage

TrajDirectionalChange(trj, nFrames = 1)

Arguments

trj

Track to calculate DC for.

nFrames

Frame delta to process: if 1, every frame is processed, if 2, every 2nd frame is processed, and so on. Default is 1.

Details

This function returns the DC for each pair of consecutive steps. Kitamura & Imafuku (2015) used the mean and the standard deviation of DC for portions of trajectories as index values of nonlinearity and irregularity respectively.

Value

The directional change (DC) in degrees between every pair of consecutive segments in the trajectory, i.e. if nFrames is 1, the returned vector will have length nrow(trj) - 2.

References

Kitamura, T., & Imafuku, M. (2015). Behavioural mimicry in flight path of Batesian intraspecific polymorphic butterfly Papilio polytes. Proceedings of the Royal Society B: Biological Sciences, 282(1809). doi:10.1098/rspb.2015.0483

Examples

set.seed(42)
trj <- TrajGenerate()
SD = mean(TrajDirectionalChange(trj))
SDDC = sd(TrajDirectionalChange(trj))