Obtain length of trajectory

Computes and returns the length of a trajectory.

getTrajectoryLength(object, id, unit = "px", round = FALSE, as_numeric = FALSE)

Arguments

object

An object of class spata2.

id

Character value. Denotes the spatial trajectory of interest.

unit

Character value. Specifies the desired unit.

round

Numeric value or FALSE. If numeric, given to digits of base::round(). Rounds transformed values before they are returned.

Value

All functions return an output vector of the same length as the input vector.

If argument unit is among validUnitsOfLengthSI() or validUnitsOfAreaSI()

the output vector is of class units. If argument unit is 'px', the output vector is a character vector or numeric vector if as_numeric is TRUE.

Details

Several functions in SPATA2 have arguments that take distance input. To specifically refer to a distance the unit must be specified. There are three ways to create valid input for these arguments.

1. In pixel:

There are two valid input options to specify the distance in pixel:

  • numeric: Single numeric values, e.g. arg_input <- c(2, 3.554, 69, 100.67). If no unit is specified the input will be interpreted as pixels.

  • character: Suffixed with 'px', e.g. arg_input <- c('2px', '3.554px', '69px', '100.67px')

Note: The unit pixel (px) is used for distances as well as for areas. If pixel refers to a distance the pixel side length is meant. If pixel refers to an area the number of pixels is meant.

2. According to the Systeme international d`unites (SI):

Specifying distances in SI units e.g. arg_input <- c('2mm', '4mm') etc. requires the input to be a character as the unit must be provided as suffix. Between the numeric value and the unit must be no empty space! Valid suffixes can be obtained using the function validUnitsOfLengthSI().

3. As vectors of class unit:

Behind the scenes SPATA2 works with the units package. Input is converted into vectors of class units. Therefore, input can be directly provided this way: arg_input <- units::set_unit(x = c(2,4), value = 'mm') Note that pixel is not a valid unit in the units package. If you want to specify the input in pixel you have to use input option 1. In pixel.