INSTINCT Code Coverage Report


Directory: src/
File: Navigation/Math/Math.hpp
Date: 2025-07-19 10:51:51
Exec Total Coverage
Lines: 92 112 82.1%
Functions: 17 24 70.8%
Branches: 120 308 39.0%

Line Branch Exec Source
1 // This file is part of INSTINCT, the INS Toolkit for Integrated
2 // Navigation Concepts and Training by the Institute of Navigation of
3 // the University of Stuttgart, Germany.
4 //
5 // This Source Code Form is subject to the terms of the Mozilla Public
6 // License, v. 2.0. If a copy of the MPL was not distributed with this
7 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
8
9 /// @file Math.hpp
10 /// @brief Simple Math functions
11 /// @author T. Topp (topp@ins.uni-stuttgart.de)
12 /// @author N. Stahl (HiWi: Elliptical integral)
13 /// @date 2023-07-04
14
15 #pragma once
16
17 #include <concepts>
18 #include <cstdint>
19 #include <optional>
20 #include <type_traits>
21 #include <Eigen/Core>
22 #include <Eigen/Dense>
23 #include <gcem.hpp>
24 #include <fmt/format.h>
25
26 #include "util/Assert.h"
27
28 namespace NAV::math
29 {
30
31 /// @brief Calculates the factorial of an unsigned integer
32 /// @param[in] n Unsigned integer
33 /// @return The factorial of 'n'
34 uint64_t factorial(uint64_t n);
35
36 /// @brief Round the number to the specified amount of digits
37 /// @param[in] value Value to round
38 /// @param[in] digits Amount of digits
39 /// @return The rounded value
40 template<std::floating_point T>
41 372830 constexpr T round(const T& value, size_t digits)
42 {
43 372830 auto factor = std::pow(10, digits);
44 372830 return std::round(value * factor) / factor;
45 }
46
47 /// @brief Round the number to the specified amount of significant digits
48 /// @param[in] value Value to round
49 /// @param[in] digits Amount of digits
50 /// @return The rounded value
51 template<std::floating_point T>
52 40 constexpr T roundSignificantDigits(T value, size_t digits)
53 {
54
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40 if (value == 0.0) { return 0.0; }
55 // LOG_DEBUG("value = {:.13e} --> Round to {} digits", value, digits);
56 39 auto absVal = gcem::abs(value);
57 39 auto log10 = static_cast<int32_t>(gcem::log10(absVal));
58
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39 auto exp = log10 + (log10 > 0 || (log10 == 0 && absVal >= 1.0));
59 39 auto fac = static_cast<T>(digits) - static_cast<T>(exp);
60 // LOG_DEBUG(" log10 = {}, exp = {}, fac = {}", log10, exp, fac);
61 39 auto factor = static_cast<T>(gcem::pow(10.0, fac));
62 // LOG_DEBUG(" factor = {:.0e} --> value * factor = {}", factor, value * factor);
63 // LOG_DEBUG(" round = {} --> ... / factor = {}", gcem::round(value * factor), gcem::round(value * factor) / factor);
64 39 return static_cast<T>(gcem::round(value * factor) / factor);
65 }
66
67 /// @brief Interprets the input integer with certain amount of Bits as Output type. Takes care of sign extension
68 /// @tparam Out Output type
69 /// @tparam Bits Size of the input data
70 /// @tparam In Input data type (needs to be bigger than the amount of Bits)
71 /// @param[in] in Number as two's complement, with the sign bit (+ or -) occupying the MSB
72 /// @return Output type
73 template<std::integral Out, size_t Bits, std::integral In>
74 3099 constexpr Out interpretAs(In in)
75 {
76 static_assert(Bits < sizeof(In) * 8);
77 static_assert(Bits < sizeof(Out) * 8);
78
79 3099 constexpr size_t N = sizeof(Out) * 8 - Bits;
80 3099 return static_cast<Out>(static_cast<Out>((in & static_cast<In>(gcem::pow(2, Bits) - 1)) << N) >> N);
81 }
82
83 /// @brief Calculates the skew symmetric matrix of the given vector.
84 /// This is needed to perform the cross product with a scalar product operation
85 /// @tparam Derived Derived Eigen Type
86 /// @param[in] a The vector
87 /// @return Skew symmetric matrix
88 /// @note See Groves (2013) equation (2.50)
89 template<typename Derived>
90 2983507 Eigen::Matrix<typename Derived::Scalar, 3, 3> skewSymmetricMatrix(const Eigen::MatrixBase<Derived>& a)
91 {
92
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2983507 INS_ASSERT_USER_ERROR(a.cols() == 1, "Given Eigen Object must be a vector");
93
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2981683 INS_ASSERT_USER_ERROR(a.rows() == 3, "Given Vector must have 3 Rows");
94
95 2982474 Eigen::Matrix<typename Derived::Scalar, 3, 3> skewMat;
96
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2977983 skewMat << 0, -a(2), a(1),
97
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2983656 a(2), 0, -a(0),
98
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2984725 -a(1), a(0), 0;
99
100 2985034 return skewMat;
101 }
102
103 /// @brief Calculates the square of a skew symmetric matrix of the given vector.
104 /// @tparam Derived Derived Eigen Type
105 /// @param[in] a The vector
106 /// @return Square of skew symmetric matrix
107 template<typename Derived>
108 Eigen::Matrix<typename Derived::Scalar, 3, 3> skewSymmetricMatrixSquared(const Eigen::MatrixBase<Derived>& a)
109 {
110 INS_ASSERT_USER_ERROR(a.cols() == 1, "Given Eigen Object must be a vector");
111 INS_ASSERT_USER_ERROR(a.rows() == 3, "Given Vector must have 3 Rows");
112
113 Eigen::Matrix<typename Derived::Scalar, 3, 3> skewMat2;
114 skewMat2 << std::pow(a(2), 2) + std::pow(a(1), 2), a(0) * a(1), a(0) * a(2),
115 a(0) * a(1), std::pow(a(2), 2) + std::pow(a(0), 2), a(1) * a(2),
116 a(0) * a(2), a(1) * a(2), std::pow(a(0), 2) + std::pow(a(1), 2);
117
118 return skewMat2;
119 }
120
121 /// @brief Calculates the matrix exponential map of the given vector.
122 /// @tparam Derived Derived Eigen Type
123 /// @param[in] v The vector
124 /// @return The matrix exponential map
125 template<typename Derived>
126 Eigen::Matrix<typename Derived::Scalar, 3, 3> expMapMatrix(const Eigen::MatrixBase<Derived>& v)
127 {
128 INS_ASSERT_USER_ERROR(v.cols() == 1, "Given Eigen Object must be a vector");
129 INS_ASSERT_USER_ERROR(v.rows() == 3, "Given Vector must have 3 Rows");
130
131 return math::skewSymmetricMatrix(v).exp();
132 }
133
134 /// @brief Calculates the quaternionic exponential map of the given vector.
135 /// @tparam Derived Derived Eigen Type
136 /// @param[in] v The vector
137 /// @return The quaternionic exponential map
138 template<typename Derived>
139 299982 Eigen::Quaternion<typename Derived::Scalar> expMapQuat(const Eigen::MatrixBase<Derived>& v)
140 {
141
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299982 INS_ASSERT_USER_ERROR(v.cols() == 1, "Given Eigen Object must be a vector");
142
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299982 INS_ASSERT_USER_ERROR(v.rows() == 3, "Given Vector must have 3 Rows");
143
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299982 Eigen::Vector3<typename Derived::Scalar> omega = 0.5 * v;
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299982 auto omegaNorm = omega.norm();
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299982 if (omegaNorm < 1e-9) { return Eigen::Quaternion<typename Derived::Scalar>::Identity(); }
147
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299982 Eigen::Vector3<typename Derived::Scalar> quatVec = omega / omegaNorm * std::sin(omegaNorm);
148
149
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299982 return { std::cos(omegaNorm), quatVec.x(), quatVec.y(), quatVec.z() };
150 }
151
152 /// @brief Calculates the right Jacobian of SO(3) which relates additive increments in the tangent space to multiplicative increments applied on the right-hand side
153 /// @param[in] phi Vector applied on the right side
154 /// @return Right Jacobian J_r
155 template<typename Derived>
156 [[nodiscard]] Eigen::Matrix3<typename Derived::Scalar> J_r(const Eigen::MatrixBase<Derived>& phi)
157 {
158 INS_ASSERT_USER_ERROR(phi.cols() == 1, "Given Eigen Object must be a vector");
159 INS_ASSERT_USER_ERROR(phi.rows() == 3, "Given Vector must have 3 Rows");
160
161 auto phiNorm = phi.norm();
162 auto phiNorm2 = phiNorm * phiNorm;
163 auto phiNorm3 = phiNorm2 * phiNorm;
164 return Eigen::Matrix3<typename Derived::Scalar>::Identity()
165 - (1.0 - std::cos(phiNorm)) / phiNorm2 * skewSymmetricMatrix(phi)
166 + (phiNorm - std::sin(phiNorm)) / phiNorm3 * skewSymmetricMatrixSquared(phi);
167 }
168
169 /// @brief Calculates the secant of a value (sec(x) = csc(pi/2 - x) = 1 / cos(x))
170 template<std::floating_point T>
171 T sec(const T& x)
172 {
173 return 1.0 / std::cos(x);
174 }
175
176 /// @brief Calculates the cosecant of a value (csc(x) = sec(pi/2 - x) = 1 / sin(x))
177 template<std::floating_point T>
178 156269 T csc(const T& x)
179 {
180 156269 return 1.0 / std::sin(x);
181 }
182
183 /// @brief Returns the sign of the given value
184 /// @param[in] val Value to get the sign from
185 /// @return Sign of the given value
186 template<typename T>
187 1343753 int sgn(const T& val)
188 {
189 1343753 return (T(0) < val) - (val < T(0));
190 }
191
192 /// @brief Calculates the state transition matrix 𝚽 limited to specified order in 𝐅𝜏ₛ
193 /// @param[in] X Matrix
194 /// @param[in] order The order of the Taylor polynom to calculate
195 /// @note See \cite Groves2013 Groves, ch. 3.2.3, eq. 3.34, p. 98
196 template<typename Derived>
197 typename Derived::PlainObject expm(const Eigen::MatrixBase<Derived>& X, size_t order)
198 {
199 INS_ASSERT_USER_ERROR(X.rows() == X.cols(), "Matrix exponential calculation only possible for n x n matrices");
200
201 typename Derived::PlainObject e_X;
202
203 if constexpr (Derived::RowsAtCompileTime == Eigen::Dynamic)
204 {
205 e_X = Eigen::MatrixBase<Derived>::Identity(X.rows(), X.cols());
206 }
207 else
208 {
209 e_X = Eigen::MatrixBase<Derived>::Identity();
210 }
211 typename Derived::PlainObject Xpower = X;
212 for (size_t i = 1; i <= order; i++)
213 {
214 e_X += Xpower / static_cast<double>(math::factorial(i));
215
216 if (i < order)
217 {
218 Xpower *= X;
219 }
220 }
221
222 return e_X;
223 }
224
225 /// @brief Find (L^T D L)-decomposition of Q-matrix via outer product method
226 /// @param[in] Qmatrix Symmetric positive definite matrix to be factored
227 /// @return L - Factor matrix (strict lower triangular)
228 /// @return D - Vector with entries of the diagonal matrix
229 /// @note See \cite deJonge1996 de Jonge 1996, Algorithm FMFAC5
230 /// @attention Consider using NAV::math::LtDLdecomp_choleskyFact() because it is faster by up to a factor 10
231 template<typename Derived>
232 std::optional<std::pair<Eigen::Matrix<typename Derived::Scalar, Derived::RowsAtCompileTime, Derived::ColsAtCompileTime>,
233 Eigen::Vector<typename Derived::Scalar, Derived::RowsAtCompileTime>>>
234 1 LtDLdecomp_outerProduct(const Eigen::MatrixBase<Derived>& Qmatrix)
235 {
236 using Eigen::seq;
237
238 1 auto n = Qmatrix.rows();
239
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1 Eigen::Matrix<typename Derived::Scalar, Derived::RowsAtCompileTime, Derived::ColsAtCompileTime> Q = Qmatrix.template triangularView<Eigen::Lower>();
240
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1 Eigen::Matrix<typename Derived::Scalar, Derived::RowsAtCompileTime, Derived::ColsAtCompileTime> L;
241
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1 Eigen::Vector<typename Derived::Scalar, Derived::RowsAtCompileTime> D;
242
243 if constexpr (Derived::RowsAtCompileTime == Eigen::Dynamic)
244 {
245
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1 L = Eigen::Matrix<typename Derived::Scalar, Eigen::Dynamic, Eigen::Dynamic>::Zero(n, n);
246
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1 D.setZero(n);
247 }
248 else
249 {
250 L = Eigen::Matrix<typename Derived::Scalar, Derived::RowsAtCompileTime, Derived::ColsAtCompileTime>::Zero();
251 D.setZero();
252 }
253
254
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4 for (Eigen::Index i = n - 1; i >= 0; i--)
255 {
256
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3 D(i) = Q(i, i);
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3 if (Q(i, i) <= 0.0) { return {}; }
258
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3 L(i, seq(0, i)) = Q(i, seq(0, i)) / std::sqrt(Q(i, i));
259
260
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6 for (Eigen::Index j = 0; j <= i - 1; j++)
261 {
262
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3 Q(j, seq(0, j)) -= L(i, seq(0, j)) * L(i, j);
263 }
264
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3 L(i, seq(0, i)) /= L(i, i);
265 }
266
267
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1 return std::make_pair(L, D);
268 1 }
269
270 /// @brief Find (L^T D L)-decomposition of Q-matrix via a backward Cholesky factorization in a bordering method formulation
271 /// @param[in] Q Symmetric positive definite matrix to be factored
272 /// @return L - Factor matrix (strict lower triangular)
273 /// @return D - Vector with entries of the diagonal matrix
274 /// @note See \cite deJonge1996 de Jonge 1996, Algorithm FMFAC6
275 template<typename Derived>
276 std::optional<std::pair<Eigen::Matrix<typename Derived::Scalar, Derived::RowsAtCompileTime, Derived::ColsAtCompileTime>,
277 Eigen::Vector<typename Derived::Scalar, Derived::RowsAtCompileTime>>>
278 2423 LtDLdecomp_choleskyFact(const Eigen::MatrixBase<Derived>& Q)
279 {
280 using Eigen::seq;
281
282 2423 auto n = Q.rows();
283
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2423 typename Derived::PlainObject L = Q.template triangularView<Eigen::Lower>();
284
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2423 Eigen::Vector<typename Derived::Scalar, Derived::RowsAtCompileTime> D;
285 2423 double cmin = 1;
286
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2409 if constexpr (Derived::RowsAtCompileTime == Eigen::Dynamic) { D.setZero(n); }
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14 else { D.setZero(); }
289
290
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67060 for (Eigen::Index j = n - 1; j >= 0; j--)
291 {
292
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959299 for (Eigen::Index i = n - 1; i >= j + 1; i--)
293 {
294
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894662 L(i, j) = (L(i, j) - L(seq(i + 1, n - 1), j).dot(L(seq(i + 1, n - 1), i))) / L(i, i);
295 }
296
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64637 double t = L(j, j) - L(seq(j + 1, n - 1), j).dot(L(seq(j + 1, n - 1), j));
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64637 if (t <= 0.0) { return {}; }
298
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64637 double c = t / L(j, j);
299 64637 cmin = std::min(c, cmin);
300
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64637 L(j, j) = std::sqrt(t);
301 }
302
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67060 for (Eigen::Index i = 0; i < n; i++)
303 {
304
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64637 L.row(i).leftCols(i) /= L(i, i);
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64637 D(i) = std::pow(L(i, i), 2.0);
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64637 L(i, i) = 1;
307 }
308
309
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2423 return std::make_pair(L, D);
310 2409 }
311
312 /// @brief Calculates the squared norm of the vector and matrix
313 ///
314 /// \anchor eq-squaredNorm \f{equation}{ \label{eq:eq-squaredNorm}
315 /// ||\mathbf{\dots}||^2_{\mathbf{Q}} = (\dots)^T \mathbf{Q}^{-1} (\dots)
316 /// \f}
317 /// @param a Vector
318 /// @param Q Covariance matrix of the vector
319 /// @return Squared norm
320 template<typename DerivedA, typename DerivedQ>
321 8 typename DerivedA::Scalar squaredNormVectorMatrix(const Eigen::MatrixBase<DerivedA>& a, const Eigen::MatrixBase<DerivedQ>& Q)
322 {
323 static_assert(DerivedA::ColsAtCompileTime == Eigen::Dynamic || DerivedA::ColsAtCompileTime == 1);
324
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8 INS_ASSERT_USER_ERROR(a.cols() == 1, "Parameter 'a' has to be a vector");
325
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8 INS_ASSERT_USER_ERROR(a.rows() == Q.rows(), "Parameter 'a' and 'Q' need to have same size");
326
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8 INS_ASSERT_USER_ERROR(Q.cols() == Q.rows(), "Parameter 'Q' needs to be quadratic");
327
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8 return a.transpose() * Q.inverse() * a;
329 }
330
331 /// @brief Calculates the cumulative distribution function (CDF) of the standard normal distribution
332 ///
333 /// \anchor eq-normalDistCDF \f{equation}{ \label{eq:eq-normalDistCDF}
334 /// \Phi(x) = \int\displaylimits_{-\infty}^x \frac{1}{\sqrt{2\pi}} \exp{\left(-\frac{1}{2} v^2\right)} \text{d}v
335 /// \f}
336 /// which can be expressed with the error function
337 /// \anchor eq-normalDistCDF-erf \f{equation}{ \label{eq:eq-normalDistCDF-erf}
338 /// \Phi(x) = \frac{1}{2} \left[ 1 + \text{erf}{\left(\frac{x}{\sqrt{2}}\right)} \right]
339 /// \f}
340 /// Using the property
341 /// \anchor eq-erf-minus \f{equation}{ \label{eq:eq-erf-minus}
342 /// \text{erf}{\left( -x \right)} = -\text{erf}{\left( x \right)}
343 /// \f}
344 /// and the complementary error function
345 /// \anchor eq-erfc \f{equation}{ \label{eq:eq-erfc}
346 /// \text{erfc}{\left( x \right)} = 1 - \text{erf}{\left( x \right)}
347 /// \f}
348 /// we can simplify equation \eqref{eq-normalDistCDF-erf} to
349 /// \anchor eq-normalDistCDF-erfc \f{equation}{ \label{eq:eq-normalDistCDF-erfc}
350 /// \begin{aligned}
351 /// \Phi(x) &= \frac{1}{2} \left[ 1 - \text{erf}{\left(-\frac{x}{\sqrt{2}}\right)} \right] \\
352 /// &= \frac{1}{2} \text{erfc}{\left(-\frac{x}{\sqrt{2}}\right)}
353 /// \end{aligned}
354 /// \f}
355 ///
356 /// @param value Value to calculate the CDF for
357 double normalCDF(double value);
358
359 /// @brief Returns the inverse square root of a matrix
360 /// @param matrix Matrix to use
361 template<typename Derived>
362 [[nodiscard]] typename Derived::PlainObject inverseSqrt(const Eigen::MatrixBase<Derived>& matrix)
363 {
364 INS_ASSERT_USER_ERROR(matrix.rows() == matrix.cols(), "Only square matrix supported");
365 if constexpr (std::is_floating_point_v<typename Derived::Scalar>)
366 {
367 return matrix.inverse().sqrt(); // Eigen::SelfAdjointEigenSolver<Eigen::MatrixX<T>>{ covMatrix }.operatorInverseSqrt();
368 }
369 else // Eigen gets problems with ceres::Jet in the .sqrt() function
370 {
371 Eigen::JacobiSVD<Eigen::MatrixX<typename Derived::Scalar>> svd(matrix.inverse(), Eigen::ComputeFullV);
372 typename Derived::PlainObject sqrtInverse = svd.matrixV() * svd.singularValues().cwiseSqrt().asDiagonal() * svd.matrixV().transpose();
373 INS_ASSERT_USER_ERROR(!sqrtInverse.hasNaN(), "The matrix is not invertible");
374 return sqrtInverse;
375 }
376 }
377
378 /// @brief Change the sign of x according to the value of y
379 /// @param[in] x input value
380 /// @param[in] y input value
381 /// @return -x or +x
382 template<typename T>
383 2612 T sign(const T& x, const T& y)
384 {
385 // similar function 'sign' in fortran
386
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2612 if (y >= 0.0)
387 {
388 498 return fabs(x);
389 }
390 2114 return -1.0 * fabs(x);
391 }
392
393 /// @brief Linear interpolation between vectors
394 /// @param a Left value
395 /// @param b Right value
396 /// @param t Multiplier. [0, 1] for interpolation
397 /// @return a + t * (b - a)
398 template<typename Derived>
399 typename Derived::PlainObject lerp(const Eigen::MatrixBase<Derived>& a, const Eigen::MatrixBase<Derived>& b, auto t)
400 {
401 return a + t * (b - a);
402 }
403
404 /// Lerp Search Result
405 struct LerpSearchResult
406 {
407 size_t l; ///< Lower bound index
408 size_t u; ///< Upper bound index (l + 1)
409 double t; ///< [0, 1] for Interpolation, otherwise Extrapolation
410 };
411
412 /// @brief Searches the value in the data container
413 /// @param[in] data Data container
414 /// @param[in] value Value to search
415 3 LerpSearchResult lerpSearch(const auto& data, const auto& value)
416 {
417 3 auto i = static_cast<size_t>(std::distance(data.begin(), std::upper_bound(data.begin(), data.end(), value)));
418
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419
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3 if (i == data.size() - 1) { i--; }
420 3 const auto& lb = data.at(i);
421 3 const auto& ub = data.at(i + 1);
422 3 double t = (value - lb) / (ub - lb);
423
424 3 return { .l = i, .u = i + 1, .t = t };
425 }
426
427 /// @brief Bilinear interpolation
428 /// @param[in] tx Distance in x component to interpolate [0, 1]
429 /// @param[in] ty Distance in y component to interpolate [0, 1]
430 /// @param[in] c00 Value for tx = ty = 0
431 /// @param[in] c10 Value for tx = 1 and ty = 0
432 /// @param[in] c01 Value for tx = 0 and ty = 1
433 /// @param[in] c11 Value for tx = ty = 1
434 ///
435 /// c01 ------ c11
436 /// | |
437 /// | |
438 /// | |
439 /// c00 ------ c10
440 ///
441 /// @note See https://www.scratchapixel.com/lessons/mathematics-physics-for-computer-graphics/interpolation/bilinear-filtering.html
442 9 auto bilinearInterpolation(const auto& tx, const auto& ty,
443 const auto& c00, const auto& c10,
444 const auto& c01, const auto& c11)
445 {
446 9 auto a = c00 * (1.0 - tx) + c10 * tx;
447 9 auto b = c01 * (1.0 - tx) + c11 * tx;
448 9 return a * (1.0 - ty) + b * ty;
449 // Alternative implementation:
450 // return (1.0 - tx) * (1.0 - ty) * c00 + tx * (1.0 - ty) * c10 + (1.0 - tx) * ty * c01 + tx * ty * c11;
451 }
452
453 /// @brief Calculates the incomplete elliptical integral of the second kind
454 /// @param[in] phi Interval bound the integration uses from 0 to phi
455 /// @param[in] m Function parameter that is integrated 1-m*sin(t)^2
456 /// @return Incomplete elliptical integral of the second kind
457 /// @note See http://www2.iap.fr/users/pichon/doc/html_xref/elliptic-es.html
458 double calcEllipticalIntegral(double phi, double m);
459
460 } // namespace NAV::math
461