mizer (version 3.4.0)

isSteady: Check whether a model is at steady state

Description

Returns TRUE if the model is at its steady state (within a specified tolerance), FALSE otherwise.

Usage

isSteady(params, tol = 0.05, effort = params@initial_effort, ...)

Value

TRUE if the model's biomass drift is within tol, FALSE

otherwise.

Arguments

params

A MizerParams object or an extension thereof.

tol

Tolerance for the relative rate of biomass change in 1/year. Defaults to 0.05 (5% change per year).

effort

The fishing effort at which to evaluate steadiness. By default the initial effort stored in params.

...

Additional arguments passed to methods.

Components are not included

Components registered with setComponent() are deliberately left out of this judgement. Their state can be any object at all, so mizer does not know what currency its entries are in and cannot form a biomass for them; and tuneSteadyState(), findSteadyState() and getStability() all hold them fixed, so a criterion that included them could be one that no mizer function is able to satisfy.

A model can therefore be isSteady() while a component of it is still changing. If your model has components with dynamics of their own, check them as well: attr(getSteadyResidual(params), "other") holds their rates of change, and mizer names any that are moving whenever it reports on the model's steady state. To settle them along with everything else, project the model with projectUntilSettled(), which advances the components like every other state variable.

Details

Steadiness is judged by computing the relative rate of change of biomass across all consumer species and the resource (see getSteadyResidual()). If the largest biomass drift is less than or equal to tol, the model is considered to be at steady state.

See Also

getSteadyResidual(), tuneSteadyState(), findSteadyState()

Examples

isSteady(NS_params)

# \donttest{
# Moving a species abundance off its steady state makes isSteady() FALSE
params <- NS_params
initialN(params)[1, ] <- initialN(params)[1, ] * 2
isSteady(params)
# }