RelativeStandardDeviationLongFunction.java

/**
 * diqube: Distributed Query Base.
 *
 * Copyright (C) 2015 Bastian Gloeckle
 *
 * This file is part of diqube.
 *
 * diqube is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.diqube.function.aggregate;

import org.diqube.data.column.ColumnType;
import org.diqube.function.AggregationFunction;
import org.diqube.function.Function;
import org.diqube.function.FunctionException;
import org.diqube.function.aggregate.result.IntermediaryResultValueIterator;
import org.diqube.function.aggregate.result.IntermediaryResultValueSink;

/**
 * Calculates the relative standard deviation of the population variance.
 * 
 * <p>
 * sd(x) / avg(x)
 *
 * @author Bastian Gloeckle
 */
@Function(name = RelativeStandardDeviationLongFunction.NAME)
public class RelativeStandardDeviationLongFunction implements AggregationFunction<Long, Double> {
  public static final String NAME = "rsd";

  private StandardDeviationLongFunction sdFunction;
  private AvgLongFunction avgFunction;

  public RelativeStandardDeviationLongFunction() {
    sdFunction = new StandardDeviationLongFunction();
    avgFunction = new AvgLongFunction();
  }

  @Override
  public String getNameLowerCase() {
    return NAME;
  }

  @Override
  public void provideConstantParameter(int idx, Object value) throws FunctionException {
    // noop
  }

  @Override
  public void addValues(ValueProvider<Long> valueProvider) {
    Long[] values = valueProvider.getValues();

    ValueProvider<Long> childValueProvider = new ValueProvider<Long>() {
      @Override
      public long size() {
        return values.length;
      }

      @Override
      public Long[] getValues() {
        return values;
      }

      @Override
      public boolean isFinalSetOfValues() {
        return valueProvider.isFinalSetOfValues();
      }
    };

    sdFunction.addValues(childValueProvider);
    avgFunction.addValues(childValueProvider);
  }

  @Override
  public void addIntermediary(IntermediaryResultValueIterator intermediary) {
    sdFunction.addIntermediary(intermediary);
    avgFunction.addIntermediary(intermediary);
  }

  @Override
  public void removeIntermediary(IntermediaryResultValueIterator intermediary) {
    sdFunction.removeIntermediary(intermediary);
    avgFunction.removeIntermediary(intermediary);
  }

  @Override
  public void populateIntermediary(IntermediaryResultValueSink res) throws FunctionException {
    sdFunction.populateIntermediary(res);
    avgFunction.populateIntermediary(res);
  }

  @Override
  public Double calculate() throws FunctionException {
    double standardDeviation = sdFunction.calculate();
    double avg = avgFunction.calculate();

    return standardDeviation / avg;
  }

  @Override
  public ColumnType getOutputType() {
    return ColumnType.DOUBLE;
  }

  @Override
  public ColumnType getInputType() {
    return ColumnType.LONG;
  }

  @Override
  public boolean needsActualValues() {
    return true;
  }
}