Mercurial > dive4elements > river
view artifacts/src/main/java/org/dive4elements/river/artifacts/math/GrubbsOutlier.java @ 8755:30b1ddadf275
(issue1801) Unify reference gauge finding code
The basic way as described in the method comment of the
determineRefGauge method is now used in the WINFOArtifact,
MainValuesService and RiverUtils.getGauge method.
RiverUtils.getGauge previously just returned the first
gauge found. While this is now a behavior change I believe
that it is always more correct then the undeterministic
behavior of the previous implmenentation.
author | Andre Heinecke <andre.heinecke@intevation.de> |
---|---|
date | Wed, 24 Jun 2015 14:07:26 +0200 |
parents | af13ceeba52a |
children | 0a5239a1e46e |
line wrap: on
line source
/* Copyright (C) 2011, 2012, 2013 by Bundesanstalt für Gewässerkunde * Software engineering by Intevation GmbH * * This file is Free Software under the GNU AGPL (>=v3) * and comes with ABSOLUTELY NO WARRANTY! Check out the * documentation coming with Dive4Elements River for details. */ package org.dive4elements.river.artifacts.math; import java.util.List; import org.apache.commons.math.MathException; import org.apache.commons.math.distribution.TDistributionImpl; import org.apache.commons.math.stat.descriptive.moment.Mean; import org.apache.commons.math.stat.descriptive.moment.StandardDeviation; import org.apache.log4j.Logger; public class GrubbsOutlier { public static final double EPSILON = 1e-5; public static final double DEFAULT_ALPHA = 0.05; private static Logger log = Logger.getLogger(GrubbsOutlier.class); protected GrubbsOutlier() { } public static Integer findOutlier(List<Double> values) { return findOutlier(values, DEFAULT_ALPHA, null); } public static Integer findOutlier( List<Double> values, double alpha, double[] stdDevResult ) { boolean debug = log.isDebugEnabled(); if (debug) { log.debug("outliers significance: " + alpha); } alpha = 1d - alpha; int N = values.size(); if (debug) { log.debug("Values to check: " + N); } if (N < 3) { return null; } Mean mean = new Mean(); StandardDeviation std = new StandardDeviation(); for (Double value: values) { double v = value.doubleValue(); mean.increment(v); std .increment(v); } double m = mean.getResult(); double s = std.getResult(); if (debug) { log.debug("mean: " + m); log.debug("std dev: " + s); } double maxZ = -Double.MAX_VALUE; int iv = -1; for (int i = N-1; i >= 0; --i) { double v = values.get(i).doubleValue(); double z = Math.abs(v - m); if (z > maxZ) { maxZ = z; iv = i; } } if (Math.abs(s) < EPSILON) { return null; } maxZ /= s; TDistributionImpl tdist = new TDistributionImpl(N-2); double t; try { t = tdist.inverseCumulativeProbability(alpha/(N+N)); } catch (MathException me) { log.error(me); return null; } t *= t; double za = ((N-1)/Math.sqrt(N))*Math.sqrt(t/(N-2d+t)); if (debug) { log.debug("max: " + maxZ + " crit: " + za); } if (stdDevResult != null) { stdDevResult[0] = std.getResult(); } return maxZ > za ? Integer.valueOf(iv) : null; } } // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :