Fit a unit-aware diameter

Parameters can carry Pint units. The model receives values with the original units, so the physics code does not need to know how the optimizer stores its internal scalar coordinates.

The fitted diameter is approximately 120 nanometers: doubling it reproduces the 240 nm observation. This scalar example demonstrates unit handling, not a scattering forward model.

120.00007629394531 nanometer

from PyMieSim import FitParameter, MeasuredData, fit_parameters, ureg

observation = MeasuredData(values=240 * ureg.nanometer)


def model(parameters):
    diameter = parameters["diameter"]
    return 2 * diameter


result = fit_parameters(
    model=model,
    observation=observation,
    parameters=[
        FitParameter(
            name="diameter",
            initial=150 * ureg.nanometer,
            bounds=(50 * ureg.nanometer, 300 * ureg.nanometer),
        )
    ],
)

print(result.parameters["diameter"])