@Override
  public void transform(Row row, PointCollector collector) throws Exception {
    if (row.isNull(0)) {
      valueArrayList.add(Double.NaN);
    } else {
      double v = Util.getValueAsDouble(row);
      if (Double.isFinite(v)) {
        valueArrayList.add(v);
      } else {
        valueArrayList.add(0d);
      }
    }
  }
This function calculates acf, and then calculates p-value of corresponding Q_LB statistics.
library-udf/src/main/java/org/apache/iotdb/library/dprofile/UDTFQLB.java