trajr (version 1.5.1)

TrajDirectionalChange: 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)

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.

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.

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))