chart2/source/model/template/HistogramCalculator.cxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  */
   9
  10 #include "HistogramCalculator.hxx"
  11
  12 #include <algorithm>
  13 #include <cmath>
  14
  15 namespace chart
  16 {
  17 HistogramCalculator::HistogramCalculator() = default;
  18
  19 void HistogramCalculator::computeBinFrequencyHistogram(const std::vector<double>& rDataPoints)
  20 {
  21     if (rDataPoints.empty())
  22         return;
  23
  24     mnBins = 1;
  25     mfBinWidth = 1.0;
  26     maBinRanges.clear();
  27     maBinFrequencies.clear();
  28
  29     // Calculate statistics
  30     double fSum = 0.0;
  31     double fSquareSum = 0.0;
  32     double fMinValue = rDataPoints[0];
  33     double fMaxValue = rDataPoints[0];
  34     sal_Int32 nValidCount = 0;
  35
  36     // Compute min and max values, ignoring non-finite values
  37     for (const auto& rValue : rDataPoints)
  38     {
  39         if (std::isfinite(rValue))
  40         {
  41             fSum += rValue;
  42             fSquareSum += rValue * rValue;
  43             fMinValue = std::min(fMinValue, rValue);
  44             fMaxValue = std::max(fMaxValue, rValue);
  45             ++nValidCount;
  46         }
  47     }
  48
  49     if (nValidCount < 2 || fMinValue == fMaxValue) // Need at least two points for variance
  50     {
  51         mnBins = 1;
  52         mfBinWidth = 1.0;
  53         maBinRanges = { { std::floor(fMinValue), std::ceil(fMinValue + 1.0) } };
  54         maBinFrequencies = { nValidCount };
  55         return;
  56     }
  57
  58     double fMean = fSum / nValidCount;
  59     double fVariance = (fSquareSum - fSum * fMean) / (nValidCount - 1);
  60     double fStdDev = std::sqrt(fVariance);
  61
  62     // Apply Scott's rule for bin width
  63     mfBinWidth = (3.5 * fStdDev) / std::cbrt(nValidCount);
  64
  65     // Calculate number of bins
  66     mnBins = static_cast<sal_Int32>(std::ceil((fMaxValue - fMinValue) / mfBinWidth));
  67     mnBins = std::max<sal_Int32>(mnBins, 1); // Ensure at least one bin
  68
  69     // Set up bin ranges
  70     maBinRanges.reserve(mnBins);
  71     double fBinStart = fMinValue;
  72
  73     for (sal_Int32 i = 0; i < mnBins; ++i)
  74     {
  75         double fBinEnd = fBinStart + mfBinWidth;
  76
  77         // Correct rounding to avoid discrepancies
  78         fBinStart = std::round(fBinStart * 100.0) / 100.0;
  79         fBinEnd = std::round(fBinEnd * 100.0) / 100.0;
  80
  81         if (i == 0)
  82         {
  83             // First bin includes the minimum value, so use closed interval [fMinValue, fBinEnd]
  84             maBinRanges.emplace_back(fMinValue, fBinEnd);
  85         }
  86         else
  87         {
  88             // Subsequent bins use half-open interval (fBinStart, fBinEnd]
  89             maBinRanges.emplace_back(fBinStart, fBinEnd);
  90         }
  91         fBinStart = fBinEnd;
  92     }
  93
  94     // Adjust the last bin end to be inclusive
  95     maBinRanges.back().second = std::max(maBinRanges.back().second, fMaxValue);
  96
  97     // Calculate frequencies
  98     maBinFrequencies.assign(mnBins, 0);
  99     for (double fValue : rDataPoints)
 100     {
 101         if (std::isfinite(fValue))
 102         {
 103             for (size_t i = 0; i < maBinRanges.size(); ++i)
 104             {
 105                 if (i == 0 && fValue >= maBinRanges[i].first && fValue <= maBinRanges[i].second)
 106                 {
 107                     maBinFrequencies[i]++;
 108                     break;
 109                 }
 110                 else if (i > 0 && fValue > maBinRanges[i].first && fValue <= maBinRanges[i].second)
 111                 {
 112                     maBinFrequencies[i]++;
 113                     break;
 114                 }
 115             }
 116         }
 117     }
 118 }
 119
 120 } //  namespace chart
 121
 122 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */