| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| |
| package org.apache.datasketches.pig.kll; |
| |
| import java.io.IOException; |
| |
| import org.apache.datasketches.kll.KllFloatsSketch; |
| import org.apache.datasketches.memory.Memory; |
| import org.apache.pig.EvalFunc; |
| import org.apache.pig.data.DataByteArray; |
| import org.apache.pig.data.Tuple; |
| |
| /** |
| * This UDF is to get a quantile value from a given sketch. A single value for a |
| * given fraction is returned. The fraction represents a normalized rank and must be |
| * from 0 to 1 inclusive. For example, the fraction of 0.5 corresponds to 50th percentile, |
| * which is the median value of the distribution (the number separating the higher half |
| * of the probability distribution from the lower half). |
| */ |
| public class GetQuantile extends EvalFunc<Float> { |
| |
| @Override |
| public Float exec(final Tuple input) throws IOException { |
| if (input.size() != 2) { |
| throw new IllegalArgumentException("expected two inputs: sketch and fraction"); |
| } |
| |
| if (!(input.get(0) instanceof DataByteArray)) { |
| throw new IllegalArgumentException("expected a DataByteArray as a sketch, got " |
| + input.get(0).getClass().getSimpleName()); |
| } |
| final DataByteArray dba = (DataByteArray) input.get(0); |
| final KllFloatsSketch sketch = KllFloatsSketch.heapify(Memory.wrap(dba.get())); |
| |
| if (!(input.get(1) instanceof Double)) { |
| throw new IllegalArgumentException("expected a double value as a fraction, got " |
| + input.get(1).getClass().getSimpleName()); |
| } |
| final double fraction = (double) input.get(1); |
| return sketch.getQuantile(fraction); |
| } |
| |
| } |