secr (version 4.4.8)

distancetotrap: Distance To Nearest Detector

Description

Compute Euclidean distance from each of a set of points to the nearest detector in an array, or return the sequence number of the detector nearest each point.

Usage

distancetotrap(X, traps)
nearesttrap(X, traps)

Arguments

X

coordinates

traps

traps object or 2-column matrix of coordinates

Value

distancetotrap returns a vector of distances (assumed to be in metres).

nearesttrap returns the index of the nearest trap.

Details

distancetotrap returns the distance from each point in X to the nearest detector in traps. It may be used to restrict the points on a habitat mask.

For traps objects with polygon detector type (polygon, polygonX), and for SpatialPolygons, the function rgeos::gDistance is used internally if the package rgeos is available (from secr 4.2.0). The method is otherwise approximate and uses only the first polygon.

See Also

make.mask

Examples

# NOT RUN {
  ## restrict a habitat mask to points within 70 m of traps  
  ## this is nearly equivalent to using make.mask with the 
  ## `trapbuffer' option
  temptrap <- make.grid()
  tempmask <- make.mask(temptrap)
  d <- distancetotrap(tempmask, temptrap)
  tempmask <- subset(tempmask, d < 70)

# }