Create or modify custom variables or functions

Custom functions are user-defined functions that can be used throughout a stock-and-flow model. custom_func() adds or changes a function. This is a convenience wrapper around update() with type = "func".

Usage

custom_func(object, name, eqn = 0, label = name, doc = "")

Arguments

object

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

name

Name of the function variable. The equation will be assigned to this name.

eqn

Equation of the function variable. A character vector. Defaults to 0.

label

Name of variable used for plotting. Defaults to the same as name.

doc

Documentation. Defaults to "".

Value

A stock-and-flow model object of class stockflow

See also

update(), discard(), change_name()

Examples

# Simple function
sfm <- stockflow() |>
  custom_func(double, eqn = "function(x) x * 2") |>
  constant(a, eqn = double(2))

# Function with defaults
sfm <- stockflow() |>
  custom_func(scale, eqn = "function(x, factor = 10) x * factor") |>
  constant(b, eqn = scale(2))

# If the logistic() function did not exist, you could create it yourself:
sfm <- stockflow() |>
  custom_func(my_logistic, eqn = "function(x, slope = 1, midpoint = .5){
   1 / (1 + exp(-slope*(x-midpoint)))
 }") |>
  constant(c_, eqn = my_logistic(2, slope = 50))