param (pmrf.param)

pmrf.param(*, default: Any = <dataclasses._MISSING_TYPE object>, as_free: bool = False, as_fixed: bool = False, constraint: AbstractConstraint | None = None, scale: float = 1.0, **kwargs) → Any

A field specifier for registering parameters within a model.

This specifier can be used when declaring custom models inheriting from pmrf.Model.

It is used to register the parameter when a model is constructed, so it is listed under pmrf.Model.named_params(). It can also be used to enforce constraints, scaling, bounds and variability within the model itself.

This simply creates a pmrf.field with a pmrf.as_param converter.

Example

Declaring a parameter with a positive constraint and built-in scale:

import pmrf as prf
from pmrf.models import Resistor, Capacitor
from pmrf.constraints import Positive

class RC(prf.Model):
    R: prf.Param = prf.param(constraint=Positive())
    C: prf.Param = prf.param(constraint=Positive(), scale=1e-12)

    def build(self) -> prf.Model:
        return Resistor(self.R) ** Capacitor(self.C)

RC(1.0, 2.0)
# RC(R=1., C=2.e-12)

RC(-1.0, 2.0)
# ValueError: out of bounds
Parameters:

  • default (Any, optional) – The default value of the parameter.

  • constraint (Optional[AbstractConstraint], optional) – The constraint to apply to the parameter. See pmrf.constraints.

  • scale (float, optional) – The scaling factor to apply, by default 1.0.

  • as_free (bool, optional) – Whether to enforce that the value is a variable parameter. If False, incoming values will keep the variability (e.g. constants will remain constants). If True, all values will be co-erced into variable parameters.

  • as_fixed (bool, optional) – Whether to enforce that the value is a fixed parameter. If False, incoming values will keep the variability (e.g. constants will remain constants). If True, all values will be wrapped in pmrf.Fixed().

  • **kwargs – Additional key-word arguments to pass to the general pmrf.field() specifier.

Returns:

An equinox field with a built-in converter for parameter rules.

Return type:

Any