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README.md  view on Meta::CPAN

  with automatic eV/nm unit handling and interpolation
- **Circular Delta residuals** — proper handling of the 0°/360° wrap in the
  Levenberg-Marquardt objective function
- **Parameter bounds & vary/fix** (`VASE::Parameter`) — logit-transformed
  bounded optimisation, fixed-parameter support
- **Global optimiser** (`VASE::Optimizer`) — Differential Evolution
  (DE/rand/1/bin) and grid search for initial parameter estimation
- **Weighted fitting** — uses measured uncertainties (sigma) from Woollam files
- **Numerical Jacobian** — configurable finite-difference step with minimum
  absolute floor
- **Plotting** — multi-angle colour-coded overlays via PDL::Graphics::Gnuplot

## Installation

From source:

```bash
perl Makefile.PL
make
make test
make install

lib/Physics/Ellipsometry/VASE.pm  view on Meta::CPAN

        my $delta_data  = $data->((3),:)->flat;
        my $delta_model = $y_fit->slice("$npts:" . (2*$npts-1));
        my $diff = $delta_model - $delta_data;
        $delta_model -= 360.0 * rint($diff / 360.0);
    }

    my $chi2 = sum(($y_data - $y_fit)**2)->sclr;
    return sqrt($chi2 / (2*$npts - $nparams));
}

# Plot raw data with model fit overlay
sub plot {
    my ($self, $fit_params, %opts) = @_;
    require PDL::Graphics::Gnuplot;

    my $data  = $self->{data};
    my $model = $self->{model};

    my $wavelength = $data->((0),:)->flat;
    my $angles     = $data->((1),:)->flat;
    my $psi_data   = $data->((2),:)->flat;