1/*
2Copyright 2018 Google Inc. All Rights Reserved.
3
4Licensed under the Apache License, Version 2.0 (the "License");
5you may not use this file except in compliance with the License.
6You may obtain a copy of the License at
7
8 http://www.apache.org/licenses/LICENSE-2.0
9
10Unless required by applicable law or agreed to in writing, software
11distributed under the License is distributed on an "AS-IS" BASIS,
12WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13See the License for the specific language governing permissions and
14limitations under the License.
15*/
16
17#include "base/misc_math.h"
18
19namespace vraudio {
20
21WorldPosition::WorldPosition() { setZero(); }
22
23WorldRotation::WorldRotation() { setIdentity(); }
24
25bool LinearLeastSquareFitting(const std::vector<float>& x_array,
26 const std::vector<float>& y_array, float* slope,
27 float* intercept, float* r_squared) {
28 // The array sizes must agree.
29 if (x_array.size() != y_array.size()) {
30 return false;
31 }
32
33 // At least two points are needed to fit a line.
34 if (x_array.size() < 2) {
35 return false;
36 }
37
38 float x_sum = 0.0f;
39 float y_sum = 0.0f;
40 float x_square_sum = 0.0f;
41 float xy_sum = 0.0f;
42
43 for (size_t i = 0; i < x_array.size(); ++i) {
44 const float x = x_array[i];
45 const float y = y_array[i];
46 x_sum += x;
47 y_sum += y;
48 x_square_sum += x * x;
49 xy_sum += x * y;
50 }
51
52 const float n_inverse = 1.0f / static_cast<float>(x_array.size());
53 const float x_mean = x_sum * n_inverse;
54 const float y_mean = y_sum * n_inverse;
55 const float x_square_mean = x_square_sum * n_inverse;
56 const float xy_mean = xy_sum * n_inverse;
57 const float x_mean_square = x_mean * x_mean;
58
59 // Prevent division by zero, which means a vertical line and the slope is
60 // infinite.
61 if (x_square_mean == x_mean_square) {
62 return false;
63 }
64
65 *slope = (xy_mean - x_mean * y_mean) / (x_square_mean - x_mean_square);
66 *intercept = y_mean - *slope * x_mean;
67
68 // Compute the coefficient of determination.
69 float total_sum_of_squares = 0.0f;
70 float residual_sum_of_squares = 0.0f;
71 for (size_t i = 0; i < x_array.size(); ++i) {
72 const float y_i = y_array[i];
73 total_sum_of_squares += (y_i - y_mean) * (y_i - y_mean);
74 const float y_fit = *slope * x_array[i] + *intercept;
75 residual_sum_of_squares += (y_fit - y_i) * (y_fit - y_i);
76 }
77
78 if (total_sum_of_squares == 0.0f) {
79 if (residual_sum_of_squares == 0.0f) {
80 // A special case where all y's are equal, where the |r_squared| should
81 // be 1.0, and the line is a perfectly horizontal line.
82 *r_squared = 1.0f;
83 return true;
84 } else {
85 // Division by zero.
86 return false;
87 }
88 }
89
90 *r_squared = 1.0f - residual_sum_of_squares / total_sum_of_squares;
91 return true;
92}
93
94} // namespace vraudio
95

source code of qtmultimedia/src/3rdparty/resonance-audio/resonance_audio/base/misc_math.cc