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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CHROMECAST_BASE_STATISTICS_WEIGHTED_MOVING_AVERAGE_H_
#define CHROMECAST_BASE_STATISTICS_WEIGHTED_MOVING_AVERAGE_H_
#include <stdint.h>
#include <deque>
#include "chromecast/base/statistics/weighted_mean.h"
namespace chromecast {
// Calculates the weighted moving average of recent points. The points
// do not need to be evenly distributed on the X axis, but the X coordinate
// is assumed to be generally increasing.
//
// Whenever a new sample is added using AddSample(), old samples whose
// x coordinates are farther than |max_x_range_| from the new sample's
// x coordinate will be removed from the average. Note that |max_x_range_|
// must be non-negative.
class WeightedMovingAverage {
public:
explicit WeightedMovingAverage(int64_t max_x_range);
WeightedMovingAverage(const WeightedMovingAverage&) = delete;
WeightedMovingAverage& operator=(const WeightedMovingAverage&) = delete;
~WeightedMovingAverage();
int64_t max_x_range() const { return max_x_range_; }
// Returns the current number of samples that are in the weighted average.
size_t num_samples() const { return samples_.size(); }
// Adds an (x, y) sample with the provided weight to the average.
// |weight| should be non-negative.
void AddSample(int64_t x, int64_t y, double weight);
// Gets the current average and standard error.
// Returns |true| if the average exists, |false| otherwise. If the average
// does not exist, |average| and |error| are not modified.
bool Average(int64_t* average, double* error) const;
// Clears all current samples from the moving average.
void Clear();
private:
struct Sample {
int64_t x;
int64_t y;
double weight;
};
const int64_t max_x_range_;
std::deque<Sample> samples_;
WeightedMean mean_;
};
} // namespace chromecast
#endif // CHROMECAST_BASE_STATISTICS_WEIGHTED_MOVING_AVERAGE_H_