Test area input

Tests if input refers to an area using international area units according to the SPATA2 area framework.

  • is_area(): Tests if input can be interpreted as an area

  • is_area_si(): Tests if input can be interpreted as an area in SI units.

  • is_area_pixel(): Tests if input can be interpreted as an area in pixel.

is_area(input, error = FALSE)

is_area_pixel(input, error = FALSE)

is_area_si(input, error = FALSE)

Arguments

input

Character vector. Elements must match the requirements of the SPATA2 area framework. See details for more information.

Value

Logical vector of the same length as input and/or an error if verbose

is TRUE.

Details

Several functions in SPATA2 have arguments that take area input. To specifically refer to an area 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 an area 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 areas in SI units e.g. arg_input = c('2mm2', '4mm2') 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 validUnitsOfAreaSI().

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 = 'mm2') 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.

Examples


library(SPATA2)

##### provide input as character vectors

# will return TRUE

is_area(input = c('2mm2', '4mm2'))

# will return FALSE

is_area(input = c('200 m2')) # space between value and unit

# will return TRUE

area_values <- c(200, 400)

area_values <- as_area(area_values, unit = "mm2")

is_area(input = area_values)

###### use units package

library(units)

area_values2 <- set_units(x = c(200, 300), value = "mm2")

is_area(area_values2)