steps: Functions to create and work with steps

In amt: Animal Movement Tools

Functions to create and work with steps

Description

step_lengths can be use to calculate step lengths of a track. direction_abs and direction_rel calculate the absolute and relative direction of steps. steps converts a ⁠track_xy*⁠ from a point representation to a step representation and automatically calculates step lengths and relative turning angles.

Usage

direction_abs(x, ...)

## S3 method for class 'track_xy'
direction_abs(
  x,
  full_circle = FALSE,
  zero_dir = "E",
  clockwise = FALSE,
  append_last = TRUE,
  lonlat = FALSE,
  ...
)

direction_rel(x, ...)

## S3 method for class 'track_xy'
direction_rel(x, lonlat = FALSE, append_last = TRUE, zero_dir = "E", ...)

step_lengths(x, ...)

## S3 method for class 'track_xy'
step_lengths(x, lonlat = FALSE, append_last = TRUE, ...)

steps_by_burst(x, ...)

## S3 method for class 'track_xyt'
steps_by_burst(x, lonlat = FALSE, keep_cols = NULL, ...)

steps(x, ...)

## S3 method for class 'track_xy'
steps(x, lonlat = FALSE, keep_cols = NULL, ...)

## S3 method for class 'track_xyt'
steps(x, lonlat = FALSE, keep_cols = NULL, diff_time_units = "auto", ...)

Arguments

x	[track_xy, track_xyt] A track created with make_track.
...	Further arguments, none implemented
full_circle	⁠[logical(1)=FALSE]⁠ If TRUE angles are returned between 0 and $2pi$, otherwise angles are between $-pi$ and $pi$.
zero_dir	⁠[character(1)='E']⁠ Indicating the zero direction. Must be either N, E, S, or W.
clockwise	⁠[logical(1)=FALSE]⁠ Should angles be calculated clock or anti-clockwise?
append_last	⁠[logical(1)=TRUE]⁠ If TRUE an NA is appended at the end of all angles.
lonlat	⁠[logical(1)=TRUE]⁠ Should geographical or planar coordinates be used? If TRUE geographic distances are calculated.
keep_cols	⁠[character(1)=NULL]{'start', 'end', 'both'}⁠ Should columns with attribute information be transferred to steps? If keep_cols = 'start' the attributes from the starting point are use, otherwise the columns from the end points are used.
diff_time_units	⁠[character(1)='auto']⁠ The unit for time differences, see ?difftime.

Details

⁠dierctions_*()⁠ returns NA for 0 step lengths.

step_lengths calculates the step lengths between points a long the path. The last value returned is NA, because no observed step is 'started' at the last point. If lonlat = TRUE, step_lengths() wraps sf::st_distance().

Value

⁠[numeric]⁠
For step_lengths() and ⁠direction_*⁠ a numeric vector.
⁠[data.frame]⁠
For steps and steps_by_burst, containing the steps.

Examples

xy <- tibble(
  x = c(1, 4, 8, 8, 12, 12, 8, 0, 0, 4, 2),
  y = c(0, 0, 0, 8, 12, 12, 12, 12, 8, 4, 2))
trk <- make_track(xy, x, y)

# append last
direction_abs(trk, append_last = TRUE)
direction_abs(trk, append_last = FALSE)

# degrees
direction_abs(trk) |> as_degree()

# full circle or not: check
direction_abs(trk, full_circle = TRUE)
direction_abs(trk, full_circle = FALSE)
direction_abs(trk, full_circle = TRUE) |> as_degree()
direction_abs(trk, full_circle = FALSE) |> as_degree()

# direction of 0
direction_abs(trk, full_circle = TRUE, zero_dir = "N")
direction_abs(trk, full_circle = TRUE, zero_dir = "E")
direction_abs(trk, full_circle = TRUE, zero_dir = "S")
direction_abs(trk, full_circle = TRUE, zero_dir = "W")

# clockwise or not
direction_abs(trk, full_circle = TRUE, zero_dir = "N", clockwise = FALSE)
direction_abs(trk, full_circle = TRUE, zero_dir = "N", clockwise = TRUE)

# Bearing (i.e. azimuth): only for lon/lat
direction_abs(trk, full_circle = FALSE, zero_dir = "N", lonlat = FALSE, clockwise = TRUE)
direction_abs(trk, full_circle = FALSE, zero_dir = "N", lonlat = TRUE, clockwise = TRUE)

amt documentation built on June 25, 2024, 1:14 a.m.