as.traj: Working with Trajects in 2D Space
In ClementCalenge/adehabitat: Analysis of Habitat Selection by Animals

Description Usage Arguments Details Value Author(s) References See Also Examples

The class traj is intended to explore trajects of animals monitored using radio-tracking.
as.traj creates an object of this class.
summary.traj returns the number of relocations for each "burst" of relocations and each animal.
plot.traj allows various graphical displays of the trajects.
getburst returns an object of class traj satisfying the specified criteria (selection of one focus animal, of a period of interest, of special "bursts" (see details)).
traj2df, and the reciprocal function df2traj respectively converts an object of class traj to an object of class data.frame, and conversely.

as.traj(id, xy, date, burst = id, ...)
## S3 method for class 'traj'
print(x, ...)
## S3 method for class 'traj'
summary(object, id = levels(object$id), date = NULL, ...)
## S3 method for class 'traj'
plot(x, id = levels(x$id), burst = levels(x$burst), date = NULL,
          asc = NULL, area = NULL,
          xlim = range(x$x), ylim = range(x$y),
          colasc = gray((256:1)/256), colpol = "green",
          addpoints = TRUE, addlines = TRUE,
          perani = TRUE, final = TRUE, ...)
getburst(x, burst = levels(x$burst),
         id = levels(x$id), date = NULL)
traj2df(x)
df2traj(df)

`id`	a factor or a character vector giving for each relocation the identity of the individual monitored in `as.traj`. a character vector containing the identity of the individuals of interest in other functions
`xy`	a data frame with 2 columns containing the x and y coordinates of the relocations
`date`	a vector of class `POSIXct` giving the date for each relocation in `as.traj`. a vector of class `POSIXct` with length 2, indicating the beginning and the end of the period of interest in other functions
`burst`	a factor or a character vector giving the identity of each "burst" of relocations in `as.traj` (e.g. the circuit id, see details). The burst level needs to be unique (two animals cannot have the same burst levels). a character vector containing the burst levels of interest in `plot.traj` and `getburst`
`x`	an object of class `traj`
`object`	an object of class `traj`
`asc`	an object of class `asc`
`area`	an object of class `area` (see `help(area)`)
`xlim`	the ranges to be encompassed by the x axis
`ylim`	the ranges to be encompassed by the y axis
`colasc`	a character vector giving the colors of the map of class `asc`
`colpol`	a character vector giving the colors of the polygon contour map, when `area` is not `NULL`
`addlines`	logical. If `TRUE`, lines joining consecutive relocations are drawn
`addpoints`	logical. If `TRUE`, points corresponding to each relocation are drawn
`perani`	logical. If `TRUE`, one plot is drawn for each level of the factor `id`, and for a given animal, the several bursts are superposed on the same plot. If `FALSE`, one plot is drawn for each level of the factor `burst`
`final`	logical. If `TRUE`, the initial and final relocations of each burst are indicated in blue and red, respectively
`df`	a data frame to be converted to the class `traj`
`...`	other optional vectors containing some variables measured at each relocation (e.g. temperature, wind, elevation, etc.) in `as.traj`. For other functions, arguments to be passed to the generic functions `plot`, `summary` and `print`

For a given individual, trajects are often sampled as "bursts" of relocations (Dunn and Gipson, 1977). For example, when an animal is monitored using radio-tracking, the data may consist of several circuits of activity (two successive relocations on one circuit are often highly autocorrelated, but the data from two circuits may be sampled at long intervals in time). These bursts are indicated by the factor burst.

An object of class traj is a data frame with one column named id, one column named x, one column named y, one column named date and one column named burst. This class therefore inherits from the class data.frame.

Clement Calenge clement.calenge@oncfs.gouv.fr

Dunn, J.E. and Gipson, P.S. (1977) Analysis of radio telemetry data in studies of home range. Biometrics. 59, 794–800.

as.POSIXct and strptime for additional information of the class POSIX.

data(puechabon)
locs <- puechabon$locs
locs[1:4,]

### Conversion of the date to the format POSIX
da <- as.character(locs$Date)
da <- as.POSIXct(strptime(as.character(locs$Date),
               "%y%m%d"))


### Creation of the object of class "traj"
(tr <- as.traj(id = locs$Name, xy = locs[,c("X", "Y")],
               date = da))
summary(tr)
plot(tr)

### Displays on maps of the study area
k <- puechabon$kasc
ele <- getkasc(k, "Elevation")
plot(tr, asc = ele)