SAMOA-58: Implementation of the standard precision, recall, and f1-score measures for each class in a multi-class setting
diff --git a/samoa-api/src/main/java/org/apache/samoa/evaluation/F1ClassificationPerformanceEvaluator.java b/samoa-api/src/main/java/org/apache/samoa/evaluation/F1ClassificationPerformanceEvaluator.java
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+package org.apache.samoa.evaluation;
+
+/*
+ * #%L
+ * SAMOA
+ * %%
+ * Copyright (C) 2014 - 2016 Apache Software Foundation
+ * %%
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * #L%
+ */
+
+
+import org.apache.samoa.instances.Instance;
+import org.apache.samoa.instances.Utils;
+import org.apache.samoa.moa.AbstractMOAObject;
+import org.apache.samoa.moa.core.Measurement;
+
+/**
+ * Created by Edi Bice (edi.bice gmail com) on 2/22/2016.
+ */
+public class F1ClassificationPerformanceEvaluator extends AbstractMOAObject implements
+ ClassificationPerformanceEvaluator {
+
+ private static final long serialVersionUID = 1L;
+ protected int numClasses;
+
+ protected long[] support;
+ protected long[] truePos;
+ protected long[] falsePos;
+ protected long[] trueNeg;
+ protected long[] falseNeg;
+
+ @Override
+ public void reset() {
+ reset(this.numClasses);
+ }
+
+ public void reset(int numClasses) {
+ this.numClasses = numClasses;
+ this.truePos = new long[numClasses];
+ this.falsePos = new long[numClasses];
+ this.trueNeg = new long[numClasses];
+ this.falseNeg = new long[numClasses];
+ for (int i = 0; i < this.numClasses; i++) {
+ this.support[i] = 0;
+ this.truePos[i] = 0;
+ this.falsePos[i] = 0;
+ this.trueNeg[i] = 0;
+ this.falseNeg[i] = 0;
+ }
+ }
+
+ @Override
+ public void addResult(Instance inst, double[] classVotes) {
+ int trueClass = (int) inst.classValue();
+ this.support[trueClass] += 1;
+ int predictedClass = Utils.maxIndex(classVotes);
+ if (predictedClass == trueClass) {
+ this.truePos[trueClass] += 1;
+ for (int i = 0; i < this.numClasses; i++) {
+ if (i!=predictedClass) this.trueNeg[i] += 1;
+ }
+ } else {
+ this.falsePos[predictedClass] += 1;
+ this.falseNeg[trueClass] += 1;
+ for (int i = 0; i < this.numClasses; i++) {
+ if (!(i==predictedClass || i==trueClass)) this.trueNeg[i] += 1;
+ }
+ }
+ }
+
+ @Override
+ public Measurement[] getPerformanceMeasurements() {
+ return getF1Measurements();
+ }
+
+ private Measurement[] getSupportMeasurements() {
+ Measurement[] measurements = new Measurement[this.numClasses];
+ for (int i = 0; i < this.numClasses; i++) {
+ String ml = String.format("class %s support", i);
+ measurements[i] = new Measurement(ml, this.support[i]);
+ }
+ return measurements;
+ }
+
+ private Measurement[] getPrecisionMeasurements() {
+ Measurement[] measurements = new Measurement[this.numClasses];
+ for (int i = 0; i < this.numClasses; i++) {
+ String ml = String.format("class %s precision", i);
+ measurements[i] = new Measurement(ml, getPrecision(i));
+ }
+ return measurements;
+ }
+
+ private Measurement[] getRecallMeasurements() {
+ Measurement[] measurements = new Measurement[this.numClasses];
+ for (int i = 0; i < this.numClasses; i++) {
+ String ml = String.format("class %s recall", i);
+ measurements[i] = new Measurement(ml, getRecall(i));
+ }
+ return measurements;
+ }
+
+ private Measurement[] getF1Measurements() {
+ Measurement[] measurements = new Measurement[this.numClasses];
+ for (int i = 0; i < this.numClasses; i++) {
+ String ml = String.format("class %s f1-score", i);
+ measurements[i] = new Measurement(ml, getF1Score(i));
+ }
+ return measurements;
+ }
+
+ @Override
+ public void getDescription(StringBuilder sb, int indent) {
+ Measurement.getMeasurementsDescription(getSupportMeasurements(), sb, indent);
+ Measurement.getMeasurementsDescription(getPrecisionMeasurements(), sb, indent);
+ Measurement.getMeasurementsDescription(getRecallMeasurements(), sb, indent);
+ Measurement.getMeasurementsDescription(getF1Measurements(), sb, indent);
+ }
+
+ private double getPrecision(int classIndex) {
+ return (double) this.truePos[classIndex] / (this.truePos[classIndex] + this.falsePos[classIndex]);
+ }
+
+ private double getRecall(int classIndex) {
+ return (double) this.truePos[classIndex] / (this.truePos[classIndex] + this.falseNeg[classIndex]);
+ }
+
+ private double getF1Score(int classIndex) {
+ double precision = getPrecision(classIndex);
+ double recall = getRecall(classIndex);
+ return 2 * (precision * recall) / (precision + recall);
+ }
+
+}
