Java tutorial
/******************************************************************************* * This file is part of OpenNMS(R). * * Copyright (C) 2010-2015 The OpenNMS Group, Inc. * OpenNMS(R) is Copyright (C) 1999-2015 The OpenNMS Group, Inc. * * OpenNMS(R) is a registered trademark of The OpenNMS Group, Inc. * * OpenNMS(R) 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. * * OpenNMS(R) 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 OpenNMS(R). If not, see: * http://www.gnu.org/licenses/ * * For more information contact: * OpenNMS(R) Licensing <license@opennms.org> * http://www.opennms.org/ * http://www.opennms.com/ *******************************************************************************/ package org.opennms.netmgt.measurements.filters.impl; import java.util.Map; import java.util.Map.Entry; import org.opennms.netmgt.measurements.api.Filter; import org.opennms.netmgt.measurements.api.FilterInfo; import org.opennms.netmgt.measurements.api.FilterParam; import com.google.common.collect.Maps; import com.google.common.collect.RowSortedTable; /** * Performs outlier removal and interpolation using R. * * @see {@link org.opennms.netmgt.measurements.filters.impl.OutlierFilterConfig} * @author jwhite */ @FilterInfo(name = "Outlier", description = "Removes outliers and replaces them with interpolated values.") public class OutlierFilter implements Filter { @FilterParam(key = "inputColumn", required = true, displayName = "Input", description = "Input column.") private String m_inputColumn; @FilterParam(key = "quantile", value = "0.95", displayName = "Quantile", description = "Quantile level. Must be > 0 and <= 100. Any values greater than the calculated percentile will be replaced with an interpolated value.") private double m_quantile; protected OutlierFilter() { } public OutlierFilter(String inputColumn, double quantile) { m_inputColumn = inputColumn; m_quantile = quantile; } @Override public void filter(RowSortedTable<Long, String, Double> qrAsTable) { // Extract the values of the input column as a primitive array final Map<Long, Double> column = qrAsTable.column(m_inputColumn); final double values[] = new double[column.size()]; int k = 0; for (Double value : column.values()) { values[k++] = value; } // Calculate the percentile org.apache.commons.math3.stat.descriptive.rank.Percentile percentileCalculator = new org.apache.commons.math3.stat.descriptive.rank.Percentile(); Double nthPercentile = percentileCalculator.evaluate(values, 100 * m_quantile); // Replace values greater than the percentile with NaNs for (Entry<Long, Double> entry : column.entrySet()) { if (!entry.getValue().isNaN() && entry.getValue() > nthPercentile) { entry.setValue(Double.NaN); } } // Perform linear interpolation on missing values linearInterpolation(qrAsTable); } public void linearInterpolation(RowSortedTable<Long, String, Double> qrAsTable) { final Map<Long, Double> column = qrAsTable.column(m_inputColumn); final Map<Long, Double> interpolatedValues = Maps.newHashMap(); Long x0 = null; for (Map.Entry<Long, Double> entry : column.entrySet()) { long x = entry.getKey(); double y = entry.getValue(); if (!Double.isNaN(y)) { // If there was a gap in values if (x0 != null && x0 != x - 1) { double y0 = column.get(x0); // Calculate the slope (m) and intercept (b) for the line // passing between the current point, and the last known value double m = (y0 - y) / (x0 - x); double b = y0 - m * x0; // Interpolate the missing values for (long xnot = x0 + 1; xnot < x; xnot++) { double ynot = m * xnot + b; interpolatedValues.put(xnot, ynot); } } // Update the index of the last known value x0 = x; } } // Update the column values column.putAll(interpolatedValues); } }