| /* |
| * Copyright 2016, Yahoo! Inc. |
| * Licensed under the terms of the Apache License 2.0. See LICENSE file at the project root for terms. |
| */ |
| |
| package com.yahoo.sketches.pig.quantiles; |
| |
| import java.io.IOException; |
| import java.util.Arrays; |
| import java.util.Comparator; |
| |
| import org.apache.pig.EvalFunc; |
| import org.apache.pig.data.DataByteArray; |
| import org.apache.pig.data.Tuple; |
| import org.apache.pig.data.TupleFactory; |
| |
| import com.yahoo.memory.Memory; |
| import com.yahoo.sketches.ArrayOfStringsSerDe; |
| import com.yahoo.sketches.quantiles.ItemsSketch; |
| |
| /** |
| * This UDF is to get a list of quantile values from an ItemsSketch<String> given a list of |
| * fractions or a number of evenly spaced intervals. The fractions represent normalized ranks 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 GetQuantilesFromStringsSketch extends EvalFunc<Tuple> { |
| |
| @Override |
| public Tuple exec(final Tuple input) throws IOException { |
| if (input.size() < 2) { |
| throw new IllegalArgumentException("expected two or more inputs: sketch and list of fractions"); |
| } |
| |
| 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 ItemsSketch<String> sketch = ItemsSketch.getInstance( |
| Memory.wrap(dba.get()), Comparator.naturalOrder(), new ArrayOfStringsSerDe()); |
| if (sketch.isEmpty()) { return null; } |
| |
| if (input.size() == 2) { |
| final Object arg = input.get(1); |
| if (arg instanceof Integer) { // number of evenly spaced intervals |
| return TupleFactory.getInstance().newTuple(Arrays.asList(sketch.getQuantiles((int) arg))); |
| } else if (arg instanceof Double) { // just one fraction |
| return TupleFactory.getInstance().newTuple(Arrays.asList(sketch.getQuantile((double) arg))); |
| } else { |
| throw new IllegalArgumentException("expected a double value as a fraction or an integer value" |
| + " as a number of evenly spaced intervals, got " + arg.getClass().getSimpleName()); |
| } |
| } |
| // more than one number - must be double fractions |
| final double[] fractions = new double[input.size() - 1]; |
| for (int i = 1; i < input.size(); i++) { |
| if (!(input.get(i) instanceof Double)) { |
| throw new IllegalArgumentException( |
| "expected a double value as a fraction, got " + input.get(i).getClass().getSimpleName()); |
| } |
| fractions[i - 1] = (double) input.get(i); |
| } |
| return TupleFactory.getInstance().newTuple(Arrays.asList(sketch.getQuantiles(fractions))); |
| } |
| |
| } |