CorrelationCoefficient: Separate class

common/CMakeLists.txt

@@ -130,6 +130,8 @@ ADD_LIBRARY(JFJochCommon STATIC
         ScalingSettings.h
         UnitCell.cpp
         UnitCell.h
+        CorrelationCoefficient.cpp
+        CorrelationCoefficient.h
 )
 
 TARGET_LINK_LIBRARIES(JFJochCommon JFJochLogger Compression JFCalibration gemmi Threads::Threads -lrt )

common/CorrelationCoefficient.cpp

@@ -0,0 +1,33 @@
+//
+// Created by leonarski_f on 18.05.2026.
+//
+
+#include <cmath>
+
+#include "CorrelationCoefficient.h"
+
+void CorrelationCoefficient::Add(double x, double y) {
+        sum_x += x;
+        sum_y += y;
+        sum_x2 += x * x;
+        sum_y2 += y * y;
+        sum_xy += x * y;
+        n_cc++;
+}
+
+double CorrelationCoefficient::GetCC() const {
+         if (n_cc < 2)
+            return NAN;
+        const double n = static_cast<double>(n_cc);
+        const double mean_x = sum_x / n;
+        const double mean_y = sum_y / n;
+
+        const double cov = sum_xy / n - mean_x * mean_y;
+        const double var_x = sum_x2 / n - mean_x * mean_x;
+        const double var_y = sum_y2 / n - mean_y * mean_y;
+
+        if (!(var_x > 0.0 && var_y > 0.0))
+            return NAN;
+
+        return cov / std::sqrt(var_x * var_y);
+}

common/CorrelationCoefficient.h

@@ -0,0 +1,17 @@
+// SPDX-FileCopyrightText: 2024 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
+// SPDX-License-Identifier: GPL-3.0-only
+
+#pragma once
+
+class CorrelationCoefficient {
+    double sum_x = 0.0;
+    double sum_y = 0.0;
+    double sum_x2 = 0.0;
+    double sum_y2 = 0.0;
+    double sum_xy = 0.0;
+    int n_cc = 0;
+public:
+    void Add(double x, double y);
+    [[nodiscard]] double GetCC() const;
+};
+

image_analysis/scale_merge/Merge.cpp

@@ -11,6 +11,7 @@
 
 #include <gemmi/reciproc.hpp>
 
+#include "../../common/CorrelationCoefficient.h"
 #include "../../common/ResolutionShells.h"
 #include "HKLKey.h"
 
@@ -170,39 +171,6 @@ std::vector<MergedReflection> MergeAll(const DiffractionExperiment &x,
     return out;
 }
 
-struct CCAccum {
-    double sum_x = 0.0;
-    double sum_y = 0.0;
-    double sum_x2 = 0.0;
-    double sum_y2 = 0.0;
-    double sum_xy = 0.0;
-    int n_cc = 0;
-    void Add(double x, double y) {
-        sum_x += x;
-        sum_y += y;
-        sum_x2 += x * x;
-        sum_y2 += y * y;
-        sum_xy += x * y;
-        n_cc++;
-    }
-
-    double GetCC() const {
-        if (n_cc < 2)
-            return NAN;
-        const double n = static_cast<double>(n_cc);
-        const double mean_x = sum_x / n;
-        const double mean_y = sum_y / n;
-
-        const double cov = sum_xy / n - mean_x * mean_y;
-        const double var_x = sum_x2 / n - mean_x * mean_x;
-        const double var_y = sum_y2 / n - mean_y * mean_y;
-
-        if (!(var_x > 0.0 && var_y > 0.0))
-            return NAN;
-
-        return cov / std::sqrt(var_x * var_y);
-    }
-};
 
 struct ShellAccum {
     int total_obs = 0;
@@ -212,8 +180,8 @@ struct ShellAccum {
     double sum_i_over_sigma = 0.0;
     int n_i_over_sigma = 0;
 
-    CCAccum cc_half;
-    CCAccum cc_ref;
+    CorrelationCoefficient cc_half;
+    CorrelationCoefficient cc_ref;
 };
 
 void CalcPossibleReflections(const DiffractionExperiment &x,
@@ -303,8 +271,8 @@ MergeStatistics MergeStats(const DiffractionExperiment &x,
 
     CalcPossibleReflections(x, cell, d_min_pad, d_max_pad, shells, acc);
 
-    CCAccum cc_half_overall;
-    CCAccum cc_ref_overall;
+    CorrelationCoefficient cc_half_overall;
+    CorrelationCoefficient cc_ref_overall;
 
     for (const auto &m: merged) {
         const auto shell = shells.GetShell(m.d);
@@ -326,6 +294,7 @@ MergeStatistics MergeStats(const DiffractionExperiment &x,
                         cc_ref_overall.Add(m.I, ref_it->second);
                     }
                 }
+
                 if (std::isfinite(m.I_half[0]) && std::isfinite(m.I_half[1])) {
                     acc[s].cc_half.Add(m.I_half[0], m.I_half[1]);
                     cc_half_overall.Add(m.I_half[0], m.I_half[1]);
@@ -342,10 +311,8 @@ MergeStatistics MergeStats(const DiffractionExperiment &x,
         for (const auto &r: reflections[i]) {
             if (key_generator.IsSystematicallyAbsent(r))
                 continue;
-
             if (r.image_scale_corr <= 0.0 || !std::isfinite(r.image_scale_corr))
                 continue;
-
             if (!AcceptReflection(r, d_min_limit_A))
                 continue;
             if (r.partiality < min_partiality)

image_analysis/scale_merge/Merge.h

@@ -10,7 +10,6 @@
 #include "../../common/Reflection.h"
 
 struct MergeStatisticsShell {
-
     float d_min = 0.0f;
     float d_max = 0.0f;
     float mean_one_over_d2 = 0;

tests/CCTest.cpp

@@ -0,0 +1,22 @@
+// SPDX-FileCopyrightText: 2024 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
+// SPDX-License-Identifier: GPL-3.0-only
+
+#include <catch2/catch_all.hpp>
+#include "../common/CorrelationCoefficient.h"
+
+TEST_CASE("CorrelationCoefficient") {
+    CorrelationCoefficient cc;
+    CHECK(std::isnan(cc.GetCC()));
+
+    cc.Add(100.0, 500.0);
+    CHECK(std::isnan(cc.GetCC()));
+
+    cc.Add(200.0, 1000.0);
+    CHECK(cc.GetCC() == Catch::Approx(1.0));
+
+    cc.Add(300.0, 1500.0);
+    CHECK(cc.GetCC() == Catch::Approx(1.0));
+
+    cc.Add(400.0, 2000.0);
+    CHECK(cc.GetCC() == Catch::Approx(1.0));
+}

tests/CMakeLists.txt

@@ -69,6 +69,7 @@ ADD_EXECUTABLE(jfjoch_test
         XDSPluginTest.cpp
         MergeScaleTest.cpp
         UnitCellTest.cpp
+        CCTest.cpp
 )
 
 target_link_libraries(jfjoch_test Catch2WithMain JFJochBroker JFJochReceiver JFJochReader JFJochWriter