@Override
  public void transform(Row row, PointCollector collector) throws Exception {
    if (row.isNull(0) || row.isNull(1)) {
      valueArrayList0.add(Double.NaN);
      valueArrayList1.add(Double.NaN);
    } else {
      valueArrayList0.add(Util.getValueAsDouble(row, 0));
      valueArrayList1.add(Util.getValueAsDouble(row, 1));
    }
  }
This function calculates cross correlation between two input series.
library-udf/src/main/java/org/apache/iotdb/library/dmatch/UDTFXCorr.java