Apply a function keeping units — keep

Helper function to apply a function to a units object and then restore the original units.

Usage

keep_units(FUN, x, ..., unit = units(x))

Arguments

FUN: the function to be applied.
x: first argument of FUN, of class units.
...: optional arguments to FUN.
unit: symbolic unit to restore after FUN.

Value

An object of class units.

Details

Provided for incompatible functions that do not preserve units. The user is responsible for ensuring the correctness of the output.

If x is not a units object and unit is not provided by the user, a warning is issued, and the output will also have no units (see examples).

Examples

x <- set_units(1:5, m)
keep_units(drop_units, x)
#> Units: [m]
#> [1] 1 2 3 4 5

# An example use case is with random number generating functions:
mu <- as_units(10, "years")
keep_units(rnorm, n = 1, x = mu)
#> 9.57062 [years]

# units can be directly specified if needed; for example, with
# `rexp()`, the units of the rate parameter are the inverse of
# the units of the output:
rate <- as_units(3, "1/year")
keep_units(rexp, n = 1, x = rate, unit = units(1/rate))
#> 0.04721004 [year]

# if `x` does not actually have units, a warning is issued,
# and the output has no units:
rate2 <- 3
keep_units(rexp, n = 1, x = rate2)
#> Warning: wrong `unit` specification.
#> [1] 0.4112932