docs: private void addPreviewMeasurementsToSum(
              List<double[]> measurementsSum, 
              Preview        preview, 
              int            numEntriesPerPreview) 
      {
          List<double[]> previewMeasurements = preview.getData();
          
          // add values for each measurement in each entry
          for (int entryIdx = 0; entryIdx < numEntriesPerPreview; entryIdx++) {
              double[] previewEntry = previewMeasurements.get(entryIdx);
              double[] sumEntry;
              
              if (measurementsSum.size() > entryIdx) {
                  sumEntry = measurementsSum.get(entryIdx);
              }
              else {
                  // initialize sum entry
                  sumEntry = new double[previewEntry.length];
                  measurementsSum.add(sumEntry);
              }
              
              // first measurement is used for indexing
              // -> simply copy from first preview
              if (sumEntry[0] == 0.0) {
                  sumEntry[0] = previewEntry[0];
              }
              
              // add measurements of current entry
              for (int measure = 1; measure < sumEntry.length; measure++) {
                  sumEntry[measure] += previewEntry[measure];
              }
          }
      }