Returns the mean vector of the turning angles, as defined by Batschelet, (1981). A unit vector is created for each turning angle in the trajectory, and the centre-of-mass/mean vector is returned.
TrajMeanVectorOfTurningAngles(trj, compass.direction = NULL)A complex number r which represents the mean vector,
Mod(r) is the length of the mean vector which varies between 0 and
1, Arg(r) is the angle.
Trajectory object.
If not NULL, step angles are calculated
relative to this angle (in radians), otherwise they are calculated relative
to the previous step angle.
According to Batschelet (1981), r may serve as a straightness index
ranging from 0 to 1, where r is the length of the mean vector of
turning angles of a trajectory with constant step length. Values of r
near 1 indicating straighter paths. Hence, r =
Mod(TrajMeanVectorOfTurningAngles(trj)), assuming that trj has a
constant step length (e.g. has been rediscretized).
Batschelet, E. (1981). Circular statistics in biology. ACADEMIC PRESS, 111 FIFTH AVE., NEW YORK, NY 10003, 1981, 388.
TrajStraightness, TrajAngles,
TrajRediscretize for resampling a trajectory to a constant
step length, TrajResampleTime for resampling a trajectory to
a constant step time.