GetVT function

Obtain VT table from Track

The VT table computes speeds, step lengths, orientations, turning angles and ancillary variables from a track. The output of this function is (typically) meant to feed the WindowSweep function.

GetVT(Data, units = "hour", skiplast = TRUE)

Arguments

• Data: a track to analyze. Must contain columns: X, Y and Time (as a POSIX object). The track class is a robust entry.
• units: the time units for the analysis; one of sec, min, hour, day.
• skiplast: filters away last step.

Returns

a data frame with the following columns: - Z.start, Z.end: the start and end locations (as complex coordinates)

• S: the step length

• Phi, Theta: absolute and turning angle, respectively

• T.start, T.end: start and time of steps (numeric - in given units)

• T.mid: temporal midpoint of the step

• dT: duration of the step

• V: approximate speed (S/dT)

• T.POSIX: the temporal midpoint of the step as a POSIX objects.

Examples

data(Simp)
plot(Simp)
Simp.VT <- GetVT(Simp)
head(Simp.VT)
# Distribution of estimated speeds
hist(Simp.VT$V, col="grey", breaks=20)
# Distribution of turning angles

if (requireNamespace("circular", quietly = TRUE)) 
   circular::rose.diag(Simp.VT$Theta, bins=24) else
     hist(Simp.VT$Theta)

See Also

WindowSweep

Author(s)

Eliezer Gurarie