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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.
#include "chromecast/base/statistics/weighted_mean.h"
#include <cmath>
namespace chromecast {
WeightedMean::WeightedMean() = default;
void WeightedMean::Reset() {
weighted_mean_ = 0.0;
variance_sum_ = 0.0;
sum_weights_ = 0.0;
sum_squared_weights_ = 0.0;
}
void WeightedMean::AddDelta(double delta, double weight) {
double old_sum_weights = sum_weights_;
sum_weights_ += weight;
// Use std::abs() to handle negative weights (ie, removing a sample).
sum_squared_weights_ += weight * std::abs(weight);
if (sum_weights_ == 0) {
weighted_mean_ = 0;
variance_sum_ = 0;
} else {
double mean_change = delta * weight / sum_weights_;
weighted_mean_ += mean_change;
variance_sum_ += old_sum_weights * delta * mean_change;
}
}
} // namespace chromecast