Jungfraujoch/image_analysis/indexing/FitProfileRadius.cpp

// SPDX-FileCopyrightText: 2025 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only

#include "FitProfileRadius.h"
#include <algorithm>  // std::nth_element
#include <cmath>      // std::fabs

std::optional<float> FitProfileRadius_MAD(const std::vector<SpotToSave>& xs) {
    std::vector<float> absx;
    absx.reserve(xs.size());
    for (const auto &s: xs) {
        if (s.indexed)
            absx.push_back(std::fabs(s.dist_ewald_sphere));
    }

    if (absx.empty())
        return std::nullopt;

    std::nth_element(absx.begin(), absx.begin() + absx.size() / 2, absx.end());
    float med;
    if (absx.size() % 2 == 1) {
        med = absx[absx.size() / 2];
    } else {
        auto it1 = absx.begin() + (absx.size() / 2 - 1);
        auto it2 = absx.begin() + (absx.size() / 2);
        float a = *it1;
        float b = *it2;
        med = 0.5f * (a + b);
    }
    // Normal consistency factor for MAD
    return 1.4826f * med;
}

std::optional<float> FitProfileRadius(const std::vector<SpotToSave>& spots) {
    float sum_squares = 0.0f;
    int count = 0;

    for (const auto &s: spots) {
        if (s.indexed) {
            sum_squares += s.dist_ewald_sphere * s.dist_ewald_sphere;
            count++;
        }
    }

    if (count == 0)
        return std::nullopt;

    auto std_dev = std::sqrt(sum_squares / count);
    return std_dev;
}