superseded_steady: Superseded names for the steady-state finders

In mizer: Dynamic Multi-Species Size Spectrum Modelling

Superseded names for the steady-state finders

Description

Neither of these names says what distinguishes the two functions, and projectToSteady() returns a different class depending on an argument. Both have been replaced:

Superseded	Use instead
steady()	tuneSteadyState()
projectToSteady()	findSteadyState(), or projectUntilSettled() for the trajectory

The distinction the new names carry is what each one holds fixed. tuneSteadyState() holds the inputs to the fish dynamics — the reproduction rate and the resource — at the values you supply while the spectra settle, and then adjusts the parameters that generate them (erepro/R_max and cc_pp) so that those held values are steady too. That is what steady() always did. findSteadyState() changes no parameter and lets reproduction, the resource and the spectra settle together, which is what projectToSteady() did.

Each of the two also gained a solver argument, so the same job can be done either by running the dynamics (solver = "project", the default and the old behaviour) or by solving the steady-state equation directly with a Newton-type root finder (solver = "newton"), which converges even at a dynamically unstable steady state.

The return_sim argument is gone from the new functions: tuneSteadyState() and findSteadyState() always return a MizerParams object and projectUntilSettled() always returns a MizerSim.

The old names are however not going away. They are thin wrappers that reproduce the old behaviour exactly, return_sim included: they do not warn and they will keep working, so existing code and old scripts run unchanged. They are not used anywhere inside mizer and should not be used in new code.

Usage

steady(
  params,
  t_max = 100,
  t_per = 1.5,
  dt = 0.1,
  t_save = dt,
  tol = 0.1 * dt,
  amplitude_tol = 0.01,
  amp_rel_tol = 0.01,
  extinction_threshold = 1e-06,
  return_sim = FALSE,
  preserve = c("reproduction_level", "erepro", "R_max"),
  progress_bar = TRUE,
  info_level = default_info_level(),
  method = c("euler", "predictor_corrector", "tr_bdf2")
)

projectToSteady(
  params,
  effort = params@initial_effort,
  distance_func = distanceSSLogN,
  t_per = 1.5,
  t_max = 100,
  dt = 0.1,
  t_save = dt,
  tol = 0.1 * t_per,
  amplitude_tol = 0.01,
  amp_rel_tol = 0.1,
  extinction_threshold = 1e-06,
  return_sim = FALSE,
  progress_bar = TRUE,
  info_level = default_info_level(),
  method = c("euler", "predictor_corrector", "tr_bdf2"),
  ...
)

Arguments

params	A MizerParams object
t_max	The maximum number of years to run the simulation. Default is 100.
t_per	The interval in years at which convergence is checked, and hence also the interval at which the trajectory is saved when return_sim = TRUE. In projectUntilSettled() these two roles have been separated into t_check and t_save.
dt	The time step to use in project().
t_save	Has no effect. It briefly controlled how finely the biomass series used for limit-cycle detection was sampled; that series is now sampled at every time step, which is what its default dt gave.
tol	The simulation stops when the relative change in the egg production RDI over t_per years is less than tol for every species.
amplitude_tol	The minimum relative biomass amplitude for a persistent oscillation to be reported as a limit cycle rather than treated as an (effectively steady) fixed point. This is a fraction of mean biomass and is kept separate from distance_tol (which measures convergence to a fixed point on a different scale). Default 0.01.
amp_rel_tol	Maximum relative change of amplitude between successive periods for the cycle to count as settled. Default 0.01.
extinction_threshold	A species is treated as going extinct, stopping the run, once its reproduction rate (RDD) falls below this fraction of its value at the start of the run. For example the default 1e-6 treats a species as extinct once its reproduction has collapsed to a millionth of its initial level. Because it is relative to the initial reproduction, a species that starts with zero reproduction is flagged immediately, and (in tuneSteadyState(), where reproduction is held constant) a healthy species is never flagged.
return_sim	If TRUE, the function returns the MizerSim object holding the result of the simulation run, saved at intervals of t_per. If FALSE (default) the function returns a MizerParams object with the "initial" slots set to the steady state.
preserve	Specifies whether the reproduction_level should be preserved (default) or the maximum reproduction rate R_max or the reproductive efficiency erepro. See setBevertonHolt() for an explanation of the reproduction_level.
progress_bar	A shiny progress object to implement a progress bar in a shiny app. Default FALSE.
info_level	Controls the amount of information messages that are shown. Higher levels lead to more messages, info_level = 0 gives silence. The default is taken from the mizer_info_level option, see default_info_level().
method	The numerical method to use for the consumer density update. See project().
effort	The fishing effort to use throughout. By default the initial effort stored in params.
distance_func	A function that will be called at every check with both the previous and the new state and that should return a number that in some sense measures the distance between the states. By default this uses the function distanceSSLogN() that you can use as a model for your own distance function.
...	Further arguments will be passed on to your distance function.

Value

A MizerParams object, or a MizerSim object if return_sim = TRUE, in either case carrying the "convergence" attribute described in projectUntilSettled().

See Also

tuneSteadyState(), findSteadyState(), projectUntilSettled()

mizer documentation built on Aug. 24, 2026, 9:08 a.m.