mt_track_id {move2}

Retrieve the column with track ids or get the number of tracks

Description

• mt_track_id() retrieve track ids

• mt_track_id(x) <- value and mt_set_track_id(x, value) replace track ids with new values, set new column to define tracks or rename track id column

• mt_n_tracks() returns the number of tracks

Usage

mt_track_id(x)

mt_track_id(x) <- value

mt_set_track_id(x, value)

mt_n_tracks(x)

Arguments

x

a move2 object

value

either a vector with new track id values, the name of the new column to define track ids as a scalar character (this column must be present in either the event or track table), or a scalar character to rename the track id column. IF value is NULL the move2 class is dropped and a object of the class sf is returned.

Details

The vector containing the new track ids must be of the same length as the event table.

To set a new column defining the track ids, this column has to be present in the event table. See examples.

When changing the track ids with new values that results in the combination of several tracks, the track attributes of these tracks are also combined. This is done by creating a lists within each column. See examples.

Value

mt_track_id returns a vector of the length of the number of locations that indicated the points belonging to one track.
mt_n_tracks returns the number of tracks.

Examples

x <- mt_read(mt_example())
mt_n_tracks(x)
unique(mt_track_id(x))
mt_track_id(x) |> table()
x <- mt_sim_brownian_motion(t = 1:10, tracks = 2) |>
  dplyr::mutate(attrib_evnt = gl(4, 5, labels = c("XX", "YY", "TT", "ZZ"))) |>
  mutate_track_data(attrib_trk = c("a", "b"))

## providing a vector with new track ids
unique(mt_track_id(x))
mt_track_id(x) <- c(rep("track_1", 10), rep("track_2", 10))
unique(mt_track_id(x))

## renaming the track id column
mt_track_id_column(x)
mt_track_id(x) <- "my_new_track_name"
mt_track_id_column(x)

## setting a new column to define track ids
## 1. when this column is present in the track table it has to be
## moved to the event table
names(mt_track_data(x))
x <- mt_as_event_attribute(x, "attrib_trk")
mt_track_id(x) <- "attrib_trk"
mt_track_id_column(x)
unique(mt_track_id(x))

## 2. using an existing column in the event table
mt_track_id(x) <- "attrib_evnt"
mt_track_id_column(x)
unique(mt_track_id(x))

## example of track data attributes being combined
m <- mt_sim_brownian_motion(1:3, tracks = letters[5:8]) |>
  mutate_track_data(sex = c("f", "f", "m", "m"), age = c(4, 4, 5, 6), old_track = track)
new_m <- m |> mt_set_track_id(c(rep("a", 6), rep("b", 6)))
mt_track_data(new_m)