| /* |
| * Copyright 2019, Verizon Media. |
| * Licensed under the terms of the Apache License 2.0. See LICENSE file at the project root for terms. |
| */ |
| |
| package com.yahoo.sketches.pig.kll; |
| |
| import java.io.IOException; |
| |
| import org.apache.pig.EvalFunc; |
| import org.apache.pig.data.DataByteArray; |
| import org.apache.pig.data.Tuple; |
| |
| import com.yahoo.memory.Memory; |
| import com.yahoo.sketches.kll.KllFloatsSketch; |
| |
| /** |
| * 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); |
| } |
| |
| } |