Marius Renn | 65953da | 2012-03-27 10:44:45 -0700 | [diff] [blame] | 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 ANDROID_FILTERFW_CORE_STATISTICS_H |
| 18 | #define ANDROID_FILTERFW_CORE_STATISTICS_H |
| 19 | |
| 20 | namespace android { |
| 21 | namespace filterfw { |
| 22 | |
| 23 | // An incrementally-constructed Normal distribution. |
| 24 | class IncrementalGaussian { |
| 25 | public: |
| 26 | IncrementalGaussian(); |
| 27 | |
| 28 | void Add(float value); |
| 29 | |
| 30 | float NumSamples() const { return n_; } |
| 31 | float Mean() const { return mean_; } |
| 32 | float Var() const { return var_; } |
| 33 | float Std() const; |
| 34 | float Pdf(float value) const; |
| 35 | |
| 36 | private: |
| 37 | int n_; |
| 38 | float sum_x_; |
| 39 | float sum_x2_; |
| 40 | float mean_; |
| 41 | float var_; |
| 42 | float exp_denom_; |
| 43 | float pdf_denom_; |
| 44 | }; |
| 45 | |
| 46 | // Discrete-time implementation of a simple RC low-pass filter: |
| 47 | // exponentially-weighted moving average. |
| 48 | class RCFilter { |
| 49 | public: |
| 50 | explicit RCFilter(float gain) |
| 51 | : gain_(gain), n_(0), value_(0.0f) {} |
| 52 | |
| 53 | void Add(float measurement) { |
| 54 | value_ = n_++ ? gain_ * measurement + (1.0f - gain_) * value_ : measurement; |
| 55 | } |
| 56 | |
| 57 | void Reset() { n_ = 0; } |
| 58 | |
| 59 | int NumMeasurements() const { return n_; } |
| 60 | float Output() const { return value_; } |
| 61 | |
| 62 | private: |
| 63 | float gain_; |
| 64 | int n_; |
| 65 | float value_; |
| 66 | }; |
| 67 | |
| 68 | } // namespace filterfw |
| 69 | } // namespace android |
| 70 | |
| 71 | #endif // ANDROID_FILTERFW_CORE_STATISTICS_H |