Create, modify or remove custom units

A large library of units already exists, but you may want to define your own custom units. Use model_units() to add, change, or erase custom units from a stock-and-flow model. Custom units may be new base units, or may be defined in terms of other (custom) units. See ?u() for more information on the rules of specifying units. Note that units are only supported in Julia, not in R.

Usage

model_units(sfm, name, eqn = "1", doc = "", erase = FALSE, change_name = NULL)

Arguments

sfm

Stock-and-flow model, object of class sdbuildR_xmile.

name

Name of unit. A character vector.

eqn

Definition of unit. String or vector of unit definitions. Defaults to "1" to indicate a base unit not defined in terms of other units.

doc

Documentation of unit.

erase

If TRUE, remove model unit from the model. Defaults to FALSE.

change_name

New name for model unit. Defaults to NULL to indicate no change.

Value

The modified stock-and-flow object with the specified unit(s) added or removed.

See also

unit_prefixes()

Examples

sfm = xmile("Crielaard2022")
sfm = sfm %>% model_units("BMI", eqn = "kg/m^2", doc = "Body Mass Index")

# You may also use words rather than symbols for the unit definition.
# The following modifies the unit BMI:
sfm = sfm %>% model_units("BMI", eqn = "kilogram/meters^2")

# Remove unit:
sfm = sfm %>% model_units("BMI", erase = TRUE)

# Unit names may be changed to be syntactically valid and avoid overlap:
sfm = xmile() %>% model_units("C0^2")
#> Warning: The custom unit name C0^2 was modified to C0_2 to comply with Julia's syntactic rules.
#> Use sfm %>% model_units('old_name', change_name = 'new_name') to update the name in your model.