Calculates a geographic distance matrix based on a
  PresenceAbsence or a two column matrix of x(longitude) and
  y(latitude).
Arguments
- xy
 A
PresenceAbsenceobject or amatrixwith two columns (longitude, latitude).- asdist
 Logical, if
TRUEthe result will be an object of classdist, ifFALSEthe result will be an object of classmatrix.
Value
The user can choose between dist and matrix class
  object to be returned. The resulting values are in kilometres (but see the
  argument 'unit' in rdist.earth).
Details
This function basically facilitates the use of
  terra::distance on a PresenceAbsence object, allowing also
  the user to have directly a dist object. The distance is always
  expressed in meter if the coordinate reference system is
  longitude/latitude, and in map units otherwise. Map units are typically
  meter, but inspect crs(x) if in doubt.
Examples
if (FALSE) { # \dontrun{
data(PAM)
distPAM <- lets.distmat(PAM)
} # }