| /* |
| * Copyright 2015 The Android Open Source Project |
| * |
| * 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. |
| */ |
| |
| package tests.util; |
| |
| public class SummaryStatistics { |
| /** The number of values seen. */ |
| private int numValues; |
| |
| /** Sum of the values. */ |
| private double sum; |
| |
| /** Sum of the squares of the values added. */ |
| private double squaresSum; |
| |
| /** The previously added value. */ |
| private double lastValue; |
| |
| public SummaryStatistics() { |
| } |
| |
| private double square(double value) { |
| return value * value; |
| } |
| |
| /** Add a new value to the values seen. */ |
| public void add(double value) { |
| sum += value - lastValue; |
| squaresSum += square(value) - square(lastValue); |
| numValues++; |
| lastValue = value; |
| } |
| |
| /** Mean of the values seen. */ |
| public double mean() { |
| return sum / numValues; |
| } |
| |
| /** Variance of the values seen. */ |
| public double var() { |
| return (squaresSum / numValues) - square(mean()); |
| } |
| |
| /** Standard deviation of the values seen. */ |
| public double stddev() { |
| return Math.sqrt(var()); |
| } |
| |
| /** Coefficient of variation of the values seen. */ |
| public double coeffVar() { |
| return stddev() / mean(); |
| } |
| |
| public String toString() { |
| StringBuilder sb = new StringBuilder("SummaryStatistics{"); |
| sb.append("n="); |
| sb.append(numValues); |
| sb.append(",mean="); |
| sb.append(mean()); |
| sb.append(",var="); |
| sb.append(var()); |
| sb.append(",stddev="); |
| sb.append(stddev()); |
| sb.append(",coeffVar="); |
| sb.append(coeffVar()); |
| sb.append('}'); |
| return sb.toString(); |
| } |
| } |