mergeSites: Function to merge sites
In GeoLight: Analysis of Light Based Geolocator Data

Description Usage Arguments Value Author(s)

The changeLight functions provides a vector grouping the twilight times into stationary (>0) and movement (0) periods. This function was written to enable the user to merge sites based on the distance between consequtive sites. NOTE: The function requires position estimate and desicison on whether sites should be merged will be made based on the defined distance, the cutoff values and the provided positions. The analysis is this dependent on the accuracy of the position estiamtes and should be applied to positons that were estimated using a sensible sun elevation angle.

1 2	mergeSites(tFirst, tSecond, type, twl, site, degElevation, distThreshold = 250, alpha = c(0, 15), plot = TRUE)

`tFirst`	vector of sunrise/sunset times (e.g. 2008-12-01 08:30).
`tSecond`	vector of of sunrise/sunset times (e.g. 2008-12-01 17:30).
`type`	vector of either 1 or 2, defining `tFirst` as sunrise or sunset respectively.
`twl`	data.frame containing twilights and at least `tFirst`, `tSecond` and `type`
`site`	a `numerical vector` assigning each row to a particular period. Stationary periods in numerical order and values >0, migration/movement periods 0. This `vector` will be used as the initial state.
`degElevation`	the sun elevation angle (in degrees) that defines twilight (e.g. -6 for "civil twilight"). Either a single value, a `vector` with the same length as `tFirst` or `nrow(x)`.
`distThreshold`	a `numerical` value defining the threshold of the distance under which consequtive sites should be merged (in km).
`alpha`	mean and standard variation for position optimization process.
`plot`	`logical`, if TRUE a plot comparing the inital and the final site selection.