Outer probability at a set of locations

Given a utilisation distribution and a set of query points, return for each point the cumulative-volume quantile at that location: the fraction of the UD contained in cells of equal or higher density. If a query point falls on a cell whose value is 0.5 in the volume UD, the point is on the 50 %-isopleth — together with more-central cells, those cells hold half of the total distribution.

Usage

ud_outer_probability(x, ud, ...)

Arguments

x

An sf or move2 object containing the query points, or a two-column numeric matrix/data-frame of x,y coordinates in the same CRS as ud.

ud

A single-layer terra::SpatRaster holding a probability-density UD (not a volume UD — the function computes the volume transform internally).

...

Additional arguments passed to terra::extract().

Value

A numeric vector with one value per row of x: the volume quantile at each query location. NA where the location falls outside the raster or on an NA cell.

Details

Equivalent to asking "how peripheral is this location within the animal's space use?". A value near 0 means the location is at a density peak; a value near 1 means it is far out in the tail.

This is the move2 analogue of move::outerProbability(), and is a thin wrapper around ud_volume() + terra::extract().

References

Fieberg, J., & Kochanny, C. O. (2005). Quantifying home-range overlap: the importance of the utilization distribution. Journal of Wildlife Management, 69(4), 1346-1359. doi:10.2193/0022-541X(2005)69[1346:QHOTIO]2.0.CO;2

See also

ud_volume() for the underlying transform; mt_dbbmm_ud() / mt_dbgb_ud() for producing UDs.

Examples

if (FALSE) { # \dontrun{
library(move2)
library(sf)
fishers <- mt_read(mt_example())
fishers <- fishers[!st_is_empty(fishers), ]
leroy <- fishers[mt_track_id(fishers) == "M4", ][seq_len(200), ]
leroy <- st_transform(leroy, mt_aeqd_crs(leroy))

ud <- mt_dbbmm_ud(leroy, location_error = 20, raster = 100)

## outer probability at every fix along the track
op <- ud_outer_probability(leroy, ud)
summary(op)
} # }