Traj3DStraightness: Straightness of a 3D Trajectory

In JimMcL/trajr: Animal Trajectory Analysis

Straightness of a 3D Trajectory

Description

Calculates the straightness index of a 3-dimensional trajectory, D / L, where D is the beeline distance between the first and last points in the trajectory,and L is the path length travelled (Batschelet, 1981). Benhamou (2004) considers the straightness index to be a reliable measure of the efficiency of a directed walk, but inapplicable to random trajectories. The straightness index of a random walk tends towards zero as the number of steps increases, hence should only be used to compare the tortuosity of random walks consisting of a similar number of steps.

Usage

Traj3DStraightness(trj3d)

Arguments

trj3d

3-dimensional trajectory to calculate straightness of.

Details

The straightness index is also known as the net-to-gross displacement ratio. According to Batschelet (1981), this value (termed d) is an approximation of r, which is the length of the mean vector of turning angles of a constant step-length trajectory (see TrajMeanVectorOfTurningAngles and TrajRediscretize for creating a constant step-length trajectory).

Value

The straightness index of trj, which is a value between 0 (infinitely tortuous) to 1 (a straight line).

References

Batschelet, E. (1981). Circular statistics in biology. ACADEMIC PRESS, 111 FIFTH AVE., NEW YORK, NY 10003, 1981, 388.

Benhamou, S. (2004). How to reliably estimate the tortuosity of an animal's path. Journal of Theoretical Biology, 229(2), 209-220. doi:10.1016/j.jtbi.2004.03.016

See Also

Traj3DFromCoords, Traj3DDistance for trajectory distance (or displacement), and Traj3DLength for trajectory path length, Traj3DStraightness for the straightness of a 2D trajectory.

JimMcL/trajr documentation built on July 23, 2024, 2:06 a.m.