Method Derive

Filters/Statistics/vtkDescriptiveStatistics.cxx:402–548

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//------------------------------------------------------------------------------
void vtkDescriptiveStatistics::Derive(vtkStatisticalModel* modelData)
{
  auto* primaryTab = modelData ? modelData->GetTable(vtkStatisticalModel::Learned, 0) : nullptr;
  if (!primaryTab)
  {
    return;
  }

  int numDoubles = 5;
  std::string doubleNames[] = { "Standard Deviation", "Variance", "Skewness", "Kurtosis", "Sum" };

  // Create table for derived statistics
  vtkIdType nRow = primaryTab->GetNumberOfRows();
  vtkTable* derivedTab = vtkTable::New();
  vtkDoubleArray* doubleCol;
  for (int j = 0; j < numDoubles; ++j)
  {
    if (!derivedTab->GetColumnByName(doubleNames[j].c_str()))
    {
      doubleCol = vtkDoubleArray::New();
      doubleCol->SetName(doubleNames[j].c_str());
      doubleCol->SetNumberOfTuples(nRow);
      derivedTab->AddColumn(doubleCol);
      doubleCol->Delete();
    }
  }

  // Storage for standard deviation, variance, skewness,  kurtosis, sum
  std::vector<double> derivedVals(numDoubles);

  for (int i = 0; i < nRow; ++i)
  {
    double mom2 = primaryTab->GetValueByName(i, "M2").ToDouble();
    double mom3 = primaryTab->GetValueByName(i, "M3").ToDouble();
    double mom4 = primaryTab->GetValueByName(i, "M4").ToDouble();

    vtkTypeInt64 numSamples = primaryTab->GetValueByName(i, "Cardinality").ToTypeInt64();

    if (!numSamples)
    {
      derivedVals[0] = std::numeric_limits<double>::quiet_NaN();
      derivedVals[1] = std::numeric_limits<double>::quiet_NaN();
      derivedVals[2] = std::numeric_limits<double>::quiet_NaN();
      derivedVals[3] = std::numeric_limits<double>::quiet_NaN();
      derivedVals[4] = std::numeric_limits<double>::quiet_NaN();

      for (int j = 0; j < numDoubles; ++j)
      {
        derivedTab->SetValueByName(i, doubleNames[j].c_str(), derivedVals[j]);
      }

      continue;
    }

    double mean = primaryTab->GetValueByName(i, "Mean").ToDouble();

    if (mom2 * mom2 <= FLT_EPSILON * std::abs(mean))
    {