@Override
  public void beforeStart(UDFParameters parameters, UDTFConfigurations configurations)
      throws Exception {
    configurations.setAccessStrategy(new RowByRowAccessStrategy()).setOutputDataType(Type.DOUBLE);
    s = parameters.getStringOrDefault("coef", "");
    method = parameters.getStringOrDefault("method", "");
    layer = parameters.getIntOrDefault("layer", 1);
    timestamp.clear();
    value.clear();
  }
This function calculates discrete wavelet transform of an input series. Input series must be an
integer exponent of 2. Input series is treated as sampled in equal distances.
library-udf/src/main/java/org/apache/iotdb/library/frequency/UDTFDWT.java