1 /* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef _CENTRAL_TENDENCY_STATISTICS_H 18 #define _CENTRAL_TENDENCY_STATISTICS_H 19 20 #include <math.h> 21 22 // Not multithread safe 23 class CentralTendencyStatistics { 24 25 public: 26 CentralTendencyStatistics()27 CentralTendencyStatistics() : 28 mMean(NAN), mMedian(NAN), mMinimum(INFINITY), mMaximum(-INFINITY), mN(0), mM2(0), 29 mVariance(NAN), mVarianceKnownForN(0), mStddev(NAN), mStddevKnownForN(0) { } 30 ~CentralTendencyStatistics()31 ~CentralTendencyStatistics() { } 32 33 // add x to the set of samples 34 void sample(double x); 35 36 // return the arithmetic mean of all samples so far mean()37 double mean() const { return mMean; } 38 39 // return the minimum of all samples so far minimum()40 double minimum() const { return mMinimum; } 41 42 // return the maximum of all samples so far maximum()43 double maximum() const { return mMaximum; } 44 45 // return the variance of all samples so far 46 double variance() const; 47 48 // return the standard deviation of all samples so far 49 double stddev() const; 50 51 // return the number of samples added so far n()52 unsigned n() const { return mN; } 53 54 // reset the set of samples to be empty 55 void reset(); 56 57 private: 58 double mMean; 59 double mMedian; 60 double mMinimum; 61 double mMaximum; 62 unsigned mN; // number of samples so far 63 double mM2; 64 65 // cached variance, and n at time of caching 66 mutable double mVariance; 67 mutable unsigned mVarianceKnownForN; 68 69 // cached standard deviation, and n at time of caching 70 mutable double mStddev; 71 mutable unsigned mStddevKnownForN; 72 73 }; 74 75 #endif // _CENTRAL_TENDENCY_STATISTICS_H 76