buffer: Compute Buffers
In adehabitat: Analysis of Habitat Selection by Animals

Description Usage Arguments Value Author(s) See Also Examples

buffer compute buffers around a set of locations.
buffer.ani is to be used when the points can be grouped into several categories (e.g. the relocations of several animals monitored using radio-tracking; the function buffer is then applied to each animal).
buffer.line compute buffers around a line. buffer.ltraj compute buffers around one or several animals trajectories.

buffer(pts, x, dist)
buffer.ani(pts, fac, x, dist)
buffer.line(xy, x, dist)
buffer.ltraj(ltraj, x, dist, perani=FALSE)

`pts`	a data frame with two columns (x and y coordinates of the points)
`x`	either an object of class `asc` or `kasc` with the same attributes as those desired for the output, or an object of class `mapattr` (see `storemapattr`)
`dist`	a value of distance
`fac`	a factor defining the categories of the points
`xy`	a data frame containing the coordinates of the vertices of the lines
`ltraj`	an object of class `ltraj`
`perani`	logical. If `FALSE`, one buffer is computed for each burst of relocation. If `TRUE`, the buffers are computed per levels of the attribute `id`.

buffer and buffer.line return an object of class asc, with 1 for pixels located within a specified distance of given points, and NA otherwise.
buffer.ani returns a data frame of class kasc, with each column corresponding to one level of the factor fac.
buffer.ltraj returns a data frame of class kasc, with each column corresponding to one level of the attribute id of the object of class ltraj passed as argument.

Clement Calenge clement.calenge@oncfs.gouv.fr

kasc for additionnal information on objects of class kasc, asc for further information on objects of class asc, storemapattr for further information on objects of class mapattr.

data(puechabon)

# locs is the data frame containing the
# relocations of wild boars monitored by radio-tracking 
locs <- puechabon$locs

# sa is the "kasc" object of maps of the study area
sa <- puechabon$kasc

# Buffer of 500 m around all relocations
bu <- buffer(locs[,4:5], sa, 500)
image(bu)

# displays all the pixels of the study area within 500 m
# of a relocation of each monitored wild boar
buani <- buffer.ani(locs[,4:5], locs[,1], sa, 500)
image(buani)


## buffer around a trajectory
data(puechcirc)
image(buffer.ltraj(puechcirc,sa, 100))

## buffer around a line
gc <- getcontour(getkasc(sa,1))
out <- buffer.line(gc[,2:3], sa, 300)
image(out)
lines(gc[,2:3], lwd=2)