/**
* Copyright (C) 2009 - present by OpenGamma Inc. and the OpenGamma group of companies
*
* Please see distribution for license.
*/
package com.opengamma.analytics.math.statistics.descriptive;
import java.util.Arrays;
import java.util.TreeMap;
import com.opengamma.analytics.math.MathException;
import com.opengamma.analytics.math.function.Function1D;
import com.opengamma.util.ArgumentChecker;
/**
* The mode of a series of data is the value that occurs more frequently in the data set.
*/
public class ModeCalculator extends Function1D<double[], Double> {
private static final double EPS = 1e-16;
//TODO more than one value can be the mode
/**
* @param x The array of data, not null or empty
* @return The arithmetic mean
*/
@Override
public Double evaluate(final double[] x) {
ArgumentChecker.notNull(x, "x");
ArgumentChecker.isTrue(x.length > 0, "x cannot be empty");
if (x.length == 1) {
return x[0];
}
final double[] x1 = Arrays.copyOf(x, x.length);
Arrays.sort(x1);
final TreeMap<Integer, Double> counts = new TreeMap<>();
int count = 1;
for (int i = 1; i < x1.length; i++) {
if (Math.abs(x1[i] - x1[i - 1]) < EPS) {
count++;
} else {
counts.put(count, x1[i - 1]);
count = 1;
}
}
if (counts.lastKey() == 1) {
throw new MathException("Could not find mode for array; no repeated values");
}
return counts.lastEntry().getValue();
}
}