adehabitat (version 1.8.12)

NNCH: Nearest Neighbor Convex Hulls (LoCoH)

Description

NNCH computes the home range of several animals using the LoCoH family of methods.

Usage

NNCH(xy, id = NULL, k = c(10), unin = c("m", "km"),
     unout = c("m2", "ha", "km2"), status = FALSE,
     duplicates = 1, hog.limit = 500, r = NULL, a = NULL,
     min.k = NULL, max.k = NULL)

Arguments

xy

a data frame containing the coordinates of the relocations of the monitored animals

id

a factor giving the identity of the animal for each relocation

k

if defined, the Fixed k LoCoH algorithm (k-NNCH) is used; the number of nearest neighbors minus one out of which to create convex hulls

r

if defined, the Fixed r LoCoH algorithm is used; the convex hulls are created out of all points within r distance from the root points

a

if defined, the Adaptive LoCoH algorithm is used; create convex hulls from the maximum number of nearest neighbors such that the sum of their distances is less than or equal to a

unin

the units of the relocations coordinates. Either "m" for meters or "km" for kilometers

unout

the units of the output areas. Either "m2" for square meters, "km2" for square kilometers or "ha" for hectares

status

if TRUE print out occasional progress messages as we analyze the data

duplicates

a setting to determine how duplicated points are handled. If a number, duplicated points, are displaces duplicates amount in a random direction, if "delete" all but one copy of duplicated points are deleted, if

hog.limit

if less than the number of points, a slow but memory efficient algorithm is used

min.k

for use with Fixed r LoCoH and Adaptive LoCoH a "floor" for the value of k (ie. if the value of k found using the algorithm is less than min.k, set k equal to min.k)

max.k

for use with Fixed r LoCoH and Adaptive LoCoH a "ceiling" for the value of k (ie. if the value of k found using the algorithm is more than max.k, set k equal to max.k)

Value

• NNCH returns a list of class NNCH.

Warning

These functions require the package gpclib.

References

Getz, W.M. & Wilmers, C.C. (2004). A local nearest-neighbor convex-hull construction of home ranges and utilization distributions. Ecography, in press. Getz, W.M., Fortmann-Roe, S.B, Lyons, A., Ryan, S., Cross, P. (in preparation). LoCoH methods for the construction of home ranges and utilization distributions. in preparation.

See Also

NNCH.select for plotting, rasterization, conversion to shapefiles, and management of the objects of class NNCH. NNCH.area for functions computing the homerange area.

Examples

data(chamois)
xy <- chamois$locs

(nn <- NNCH(xy, k=c(6,7)))
summary(nn)
NNCH.select(nn, k=7)

## Graphical exploration
plot(nn, k=7)

## rasterization:
asc <- ascgen(chamois$locs,nrcol=100)
asc <- NNCH.asciigrid(nn, k=7, asc=asc)  
image(asc)