TrajEmax {trajr}

Trajectory straightness index, E-max

Description

Emax, the maximum expected displacement, is a single-valued measure of straightness defined by (Cheung, Zhang, Stricker, & Srinivasan, 2007). Emax-a is a dimensionless, scale-independent measure of the maximum possible expected displacement. Emax-b is Emax-a * mean step length, and gives the maximum possible expected displacement in spatial units. Values closer to 0 are more sinuous, while larger values (approaching infinity) are straighter.

Usage

TrajEmax(trj, eMaxB = FALSE, compass.direction = NULL)

Arguments

trj

Trajectory to be analysed.

eMaxB

If TRUE, calculates and returns Emax-b, otherwise returns Emax-a.

compass.direction

if not NULL, turning angles are calculated for a directed walk, assuming the specified compass direction (in radians). Otherwise, a random walk is assumed.

Value

Emax (-a or -b) for trj.

References

Cheung, A., Zhang, S., Stricker, C., & Srinivasan, M. V. (2007). Animal navigation: the difficulty of moving in a straight line. Biological Cybernetics, 97(1), 47-61. doi:10.1007/s00422-007-0158-0