Struct ExactTwoArmRatioModel 

pub struct ExactTwoArmRatioModel { /* private fields */ }

Maps a true-energy transmission model into measured detector-bin ratios.

For a fixed response matrix R and fixed incident fluence weights F (F_j = w_j ε(E_j) Φ(E_j) — detector efficiency folded in, pipeline-map R5·7), the model supplied to the joint-Poisson objective is evaluated as

T_eff,i = sum_j F_j T_j R_ij / sum_j F_j R_ij.

The open and sample arms are therefore broadened separately. This is not the invalid post-hoc shortcut R[T].

Dead-bin precondition

A detector bin whose open-arm expectation sum_j F_j R_ij is at or below the pivot floor is a dead bin: the ratio is undefined there, so evaluate fills it with T_eff = 1.0 and analytical_jacobian zeroes its row. That filler is harmless only when the caller guarantees dead bins carry no observed counts — a joint-Poisson objective then ignores the bin entirely (its profiled rate is zero). Callers fitting observed data MUST enforce that invariant before constructing this model, as fit_counts_joint_poisson does with its occupied-bin pre-check: observed counts in a dead bin would otherwise be silently compared against an arbitrary T = 1 instead of raising an error.

Implementations

impl ExactTwoArmRatioModel

pub fn new( inner: Box<dyn FitModel>, response: DetectorBinResponseMatrix, incident_fluence_weights: &[f64], ) -> Result<Self, FittingError>

Build the reusable fixed-response model.

pub fn open_expectation(&self) -> &[f64]

Expected open-arm source shape in detector-bin order.

Trait Implementations

impl FitModel for ExactTwoArmRatioModel

fn evaluate(&self, params: &[f64]) -> Result<Vec<f64>, FittingError>

Evaluate the model for the given parameters.

fn analytical_jacobian( &self, params: &[f64], free_param_indices: &[usize], _y_current: &[f64], ) -> Option<FlatMatrix>

Optionally provide an analytical Jacobian.