Compute Turning Angles - Deprecated

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Description

angles computes the turning angles (in radians) between consecutive moves from an object of class traj. See examples for a clearer definition.

Usage

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angles(x, id = levels(x$id), burst = levels(x$burst),
       date = NULL, slsp =  c("remove", "missing"))

Arguments

x

an object of class traj

id

a character vector giving the identity of the animals for which the angles are to be computed

burst

a character vector giving the identity of the circuits for which the angles are to be computed (see traj)

date

a vector of class POSIXct of length 2 (beginning, end) delimiting the period of interest

slsp

a character string. If "remove", successive relocations located at the same place are replaced by a single relocation, allowing the computation of the angles. If "missing", a missing value is returned for the angles when successive relocations located at the same place.

Value

Returns a data frame with the following components:

id

the identity of the animal

x

the x coordinate of the relocation at which the angle is computed

y

the y coordinate of the relocation at which the angle is computed

date

a vector of class POSIXct, giving the date at which the relocation has been taken

burst

the id of the circuit (see help(traj))

angles

the turning angles between the successive moves.

Note

The function angles is deprecated. The class ltraj computes the turning angles automatically (see ltraj).

Author(s)

Clement Calenge clement.calenge@oncfs.gouv.fr

References

Turchin, P. (1998) Quantitative analysis of movement. Measuring and modeling population redistribution in animals and plants. Sunderland, Massachusetts: Sinauer Associates.

See Also

speed for computation of movement speeds, traj for additional information about objects of class traj

Examples

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## Not run: 
## loads an object of class "traj"
data(puechcirc)
puechcir <- ltraj2traj(puechcirc)
puechcir

## Gets a part of the trajectory of the wild boar named
## CH93 and draws it
## Also displays the turning angles
toto <- puechcir[2:5,]
plot(toto$x, toto$y, asp = 1, ylim = c(3158300, 3158550),
     pch = 16,
     main = "Turning angles between\nthree consecutive moves",
     xlab="X", ylab="Y")
lines(toto$x, toto$y)
lines(c(toto$x[2], 700217.6),
      c(toto$y[2], 3158310), lty=2)
lines(c(toto$x[3],700289),
      c(toto$y[3],3158546), lty=2)
ang1x <- c(700234.8, 700231.9, 700231, 700233.7, 700238.8, 700243.2)
ang1y <- c(3158332, 3158336, 3158341, 3158347, 3158350, 3158350)
ang2x <- c(700283.3, 700278.8, 700275.4, 700272.4, 700271.2, 700271.6,
           700274.7)
ang2y <- c(3158522, 3158522, 3158520, 3158517, 3158514, 3158508, 3158504)
lines(ang1x, ang1y)
lines(ang2x, ang2y)
text(700216.1, 3158349, expression(theta[1]), cex=2)
text(700247.7, 3158531, expression(theta[2]), cex=2)
text(c(700301, 700231), c(3158399, 3158487),
     c("Beginning", "End"), pos=4)



## Computation of the turning angles with real data
## on wild boars
plot(puechcir)
ang <- angles(puechcir)

## The angles are in the column angles:
ang[1:4,]

## End(Not run)

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