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/*
* Copyright (C) 2011 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.
*/
#ifndef _CENTRAL_TENDENCY_STATISTICS_H
#define _CENTRAL_TENDENCY_STATISTICS_H
#include <math.h>
// Not multithread safe
class CentralTendencyStatistics {
public:
CentralTendencyStatistics() :
mMean(NAN), mMedian(NAN), mMinimum(INFINITY), mMaximum(-INFINITY), mN(0), mM2(0),
mVariance(NAN), mVarianceKnownForN(0), mStddev(NAN), mStddevKnownForN(0) { }
~CentralTendencyStatistics() { }
// add x to the set of samples
void sample(double x);
// return the arithmetic mean of all samples so far
double mean() const { return mMean; }
// return the minimum of all samples so far
double minimum() const { return mMinimum; }
// return the maximum of all samples so far
double maximum() const { return mMaximum; }
// return the variance of all samples so far
double variance() const;
// return the standard deviation of all samples so far
double stddev() const;
// return the number of samples added so far
unsigned n() const { return mN; }
// reset the set of samples to be empty
void reset();
private:
double mMean;
double mMedian;
double mMinimum;
double mMaximum;
unsigned mN; // number of samples so far
double mM2;
// cached variance, and n at time of caching
mutable double mVariance;
mutable unsigned mVarianceKnownForN;
// cached standard deviation, and n at time of caching
mutable double mStddev;
mutable unsigned mStddevKnownForN;
};
#endif // _CENTRAL_TENDENCY_STATISTICS_H
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