ahull_track {alphahull}R Documentation

alpha-convex hull calculation of tracking data


This function approximates the \alpha-convex hull of tracking data and returns a list of geom_path objects of the boundary.


ahull_track(x, y = NULL, alpha, nps = 10000, sc = 100)


x, y

The x and y arguments provide the x and y coordinates of a set of points. Alternatively, a single argument x can be provided, see Details.


Value of \alpha.


Number of points to generate in each segment connecting two locations, see Details


Scale factor.


An attempt is made to interpret the arguments x and y in a way suitable for computing the \alpha-convex hull. Any reasonable way of defining the coordinates is acceptable, see xy.coords.

Increase nps if the trajectory is not contained in the computed estimator.


A list of geom_path objects defining the boundary of the \alpha-convex


Cholaquidis, A., Fraiman, R., Lugosi, G. and Pateiro-Lopez, B. (2014) Set estimation from reflected Brownian motion. arXiv:1411.0433.

Wikelski, M., and Kays, R. (2014). Movebank: archive, analysis and sharing of animal movement data. World Wide Web electronic publication.


## Not run: 
# Data from Movebank
# Study Name: Dunn Ranch Bison Tracking Project
# Principal Investigator: Stephen Blake, Randy Arndt, Doug Ladd
# Max Planck Institute for Ornithology Radolfzell Germany
study <- "Dunn Ranch Bison Tracking Project" 
cainfo <- system.file("CurlSSL", "cacert.pem", package = "RCurl")
options(RCurlOptions = list(verbose = FALSE, capath = cainfo, ssl.verifypeer = FALSE))
# Login to movebank (first create the login object) 
curl <- movebankLogin(username = "xxx", password = "zzz") 
# Downloads study stored in Movebank
track <- getMovebankData(study = study, login = curl) 
dat <- track@data[track@data[, "deployment_id"] == 13848432,]
# Map of animal locations 
bbox <- ggmap::make_bbox(dat[,"location_long"], dat[,"location_lat"], f = 0.3) 
map_loc <- get_map(location = bbox, source = "google", maptype = 'satellite')  
map <- ggmap(map_loc, extent = 'panel', maprange=FALSE) 
p <- map + geom_path(data = dat, aes(x = location_long, y = location_lat), col=2, size=0.3)
ah_gp <- ahull_track(x = dat[, c("location_long", "location_lat")], alpha = 0.005)
p + ah_gp

## End(Not run)

[Package alphahull version 2.5 Index]