model_units: Create, modify or remove custom units

In sdbuildR: Easily Build, Simulate, and Visualise Stock-and-Flow Models

Create, modify or remove custom units

Description

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

A stock-and-flow model object of class sdbuildR_xmile

See Also

unit_prefixes()

Examples

# Units are only supported with Julia
sfm <- xmile("Crielaard2022")
sfm <- model_units(sfm, "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 <- model_units(sfm, "BMI", eqn = "kilogram/meters^2")

# Remove unit:
sfm <- model_units(sfm, "BMI", erase = TRUE)

# Unit names may be changed to be syntactically valid and avoid overlap:
sfm <- model_units(xmile(), "C0^2")

sdbuildR documentation built on Nov. 19, 2025, 5:07 p.m.