Flags defunct clusters at the end of a track
flag_defunct_clusters(x, zeta, eta, theta, ...)# S3 method for track_xyt
flag_defunct_clusters(x, zeta, eta, theta, ...)
Returns x (a track_xyt) with a flagging column added
(x$defunct_cluster_).
[track_xyt] A track_xyt object.
[numeric] See details.
[numeric] See details.
[numeric] See details.
Addtional arguments. None currently implemented.
Brian J. Smith and Johannes Signer, based on code by Tal Avgar
Locations at the end of a trajectory may represent a dropped collar or an animal mortality. In some cases, the device may be recording locations for quite some time that are not biologically meaningful. This function aims to flag those locations at the end of the trajectory that belong to a mortality (or similar) cluster. The first location at the cluster remains unflagged, but all subsequent locations are flagged.
The algorithm detects steps that represent zero movement, within a precision
threshold given by zeta. That is, if zeta = 5 (units determined by CRS;
typically meters), all points that differ by less than 5 will be considered
zero movement. Consecutive steps of zero movement (within the tolerance) form
a cluster. The parameter eta gives the cutoff for the minimum number of
zero steps to be considered a cluster. Finally, the algorithm requires that
clusters persist without a non-zero step for a minimum amount of time, given
by theta.
flag_duplicates(),
flag_fast_steps(),
flag_roundtrips()