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Change variable type

Source: R/update.R
change_type.Rd

Change the type of a variable in a stock-and-flow model.

Usage

change_type(object, name, new_type)

Arguments

object

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

name

Variable name. Accepts a bare symbol (e.g., population), a string ("population"), or a vector via c() (e.g., c(a, b) or c("a", "b")). Use !! to inject from a variable.

new_type

New variable type; one of 'stock', 'flow', 'constant', 'aux', 'gf', or 'func'. Character vector of the same length as name.

Value

A stock-and-flow model object of class stockflow with the variable type changed throughout the model. Note that changing the type may result in changes to other properties (e.g., a flow must have "to" and/or "from" properties, so these will be added if not already present), and may require changes to the equations of connected variables.

See also

update()

Examples

# Start with a simple predator-prey model
sfm <- stockflow("predator_prey")

# Change the birth rate of predators from a constant to an auxiliary
sfm <- change_type(sfm, delta, new_type = "aux")

# This allows us to introduce time-dependence in the birth rate
# (e.g., seasonality with a sine function)
sfm <- sfm |>
  update(delta, eqn = 0.025 + 0.01 * sin(2 * pi * t / 12))
sim <- simulate(sfm)
plot(sim)