Merge pull request #267 from lasp/feature/add-interpolation-functions

Feature/add interpolation functions

Author: patkenneally

src/architecture/utilities/bilinearInterpolation.hpp

@@ -0,0 +1,58 @@
+/*
+ ISC License
+
+ Copyright (c) 2024, Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder
+
+ Permission to use, copy, modify, and/or distribute this software for any
+ purpose with or without fee is hereby granted, provided that the above
+ copyright notice and this permission notice appear in all copies.
+
+ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+ */
+
+#ifndef BILINEARINTERPOLATION_H
+#define BILINEARINTERPOLATION_H
+
+#include <cassert>
+
+/*! This function uses bilinear interpolation to solve for the value of an unknown function of two variables f(x,y)
+ at the point (x,y).
+@return double
+@param x1 Data point x1
+@param x2 Data point x2
+@param y1 Data point y1
+@param y2 Data point y2
+@param z11 Function value at point (x1, y1)
+@param z12 Function value at point (x1, y2)
+@param z21 Function value at point (x2, y1)
+@param z22 Function value at point (x2, y2)
+@param x Function x coordinate for interpolation
+@param y Function y coordinate for interpolation
+*/
+double bilinearInterpolation(double x1,
+                             double x2,
+                             double y1,
+                             double y2,
+                             double z11,
+                             double z12,
+                             double z21,
+                             double z22,
+                             double x,
+                             double y) {
+
+    assert(x1 < x && x < x2);
+    assert(y1 < y && y < y2);
+
+    return 1 / ((x2 - x1) * (y2 - y1)) * (z11 * (x2 - x) * (y2 - y) + z21 * (x - x1) * (y2 - y)
+                                          + z12 * (x2 - x) * (y - y1)
+                                          + z22 * (x - x1) * (y - y1));
+}
+
+#endif // BILINEARINTERPOLATION_H

src/architecture/utilities/linearInterpolation.hpp

@@ -0,0 +1,41 @@
+/*
+ ISC License
+
+ Copyright (c) 2024, Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder
+
+ Permission to use, copy, modify, and/or distribute this software for any
+ purpose with or without fee is hereby granted, provided that the above
+ copyright notice and this permission notice appear in all copies.
+
+ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+ */
+
+#ifndef LINEARINTERPOLATION_H
+#define LINEARINTERPOLATION_H
+
+#include <cassert>
+
+/*! This function uses linear interpolation to solve for the value of an unknown function of a single variables f(x)
+ at the point x.
+@return double
+@param x1 Data point x1
+@param x2 Data point x2
+@param y1 Function value at point x1
+@param y2 Function value at point x2
+@param x Function x coordinate for interpolation
+*/
+double linearInterpolation(double x1, double x2, double y1, double y2, double x) {
+
+    assert(x1 <  x && x < x2);
+
+    return y1 * (x2 - x) / (x2 - x1) + y2 * (x - x1) / (x2 - x1);
+}
+
+#endif // LINEARINTERPOLATION_H

src/architecture/utilities/tests/CMakeLists.txt

@@ -26,6 +26,14 @@ add_executable(test_signalProcessing test_signalProcessing.cpp)
 target_link_libraries(test_signalProcessing GTest::gtest_main)
 target_link_libraries(test_signalProcessing ArchitectureUtilities)
 
+add_executable(test_linearInterpolation test_linearInterpolation.cpp)
+target_link_libraries(test_linearInterpolation GTest::gtest_main)
+target_link_libraries(test_linearInterpolation ArchitectureUtilities)
+
+add_executable(test_bilinearInterpolation test_bilinearInterpolation.cpp)
+target_link_libraries(test_bilinearInterpolation GTest::gtest_main)
+target_link_libraries(test_bilinearInterpolation ArchitectureUtilities)
+
 if(CMAKE_HOST_SYSTEM_PROCESSOR STREQUAL "arm64" AND CMAKE_GENERATOR STREQUAL "Xcode")
     set(CMAKE_GTEST_DISCOVER_TESTS_DISCOVERY_MODE PRE_TEST)
 endif()
@@ -37,3 +45,5 @@ gtest_discover_tests(test_saturate)
 gtest_discover_tests(test_geodeticConversion)
 gtest_discover_tests(test_rigidBodyKinematics)
 gtest_discover_tests(test_signalProcessing)
+gtest_discover_tests(test_linearInterpolation)
+gtest_discover_tests(test_bilinearInterpolation)

src/architecture/utilities/tests/test_bilinearInterpolation.cpp

@@ -0,0 +1,49 @@
+/*
+ ISC License
+
+ Copyright (c) 2024, Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder
+
+ Permission to use, copy, modify, and/or distribute this software for any
+ purpose with or without fee is hereby granted, provided that the above
+ copyright notice and this permission notice appear in all copies.
+
+ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+ */
+
+#include "architecture/utilities/bilinearInterpolation.hpp"
+#include <gtest/gtest.h>
+#include <random>
+
+std::random_device rd;
+std::default_random_engine generator(rd());
+std::uniform_real_distribution<double> valueDistribution(-10, 10);
+std::uniform_real_distribution<double> boundDistribution(0, 2);
+
+TEST(BilinearInterpolationTest, HandlesNormalInputs) {
+    double x = valueDistribution(generator);
+    double x1 = x - boundDistribution(generator);
+    double x2 = x + boundDistribution(generator);
+
+    double y = valueDistribution(generator);
+    double y1 = y - boundDistribution(generator);
+    double y2 = y + boundDistribution(generator);
+
+    double z11 = valueDistribution(generator);
+    double z12 = valueDistribution(generator);
+    double z21 = valueDistribution(generator);
+    double z22 = valueDistribution(generator);
+
+    // Bilinearly interpolate to solve for z
+    double z = 1 / ((x2 - x1) * (y2 - y1)) * (z11 * (x2 - x) * (y2 - y) + z21 * (x - x1) * (y2 - y)
+                                          + z12 * (x2 - x) * (y - y1)
+                                          + z22 * (x - x1) * (y - y1));
+
+    EXPECT_EQ(bilinearInterpolation(x1, x2, y1, y2, z11, z12, z21, z22, x, y), z);
+}

src/architecture/utilities/tests/test_linearInterpolation.cpp

@@ -0,0 +1,42 @@
+/*
+ ISC License
+
+ Copyright (c) 2024, Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder
+
+ Permission to use, copy, modify, and/or distribute this software for any
+ purpose with or without fee is hereby granted, provided that the above
+ copyright notice and this permission notice appear in all copies.
+
+ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+ */
+
+#include "architecture/utilities/linearInterpolation.hpp"
+#include <gtest/gtest.h>
+#include <random>
+
+std::random_device rd;
+std::default_random_engine generator(rd());
+std::uniform_real_distribution<double> valueDistribution(-10, 10);
+std::uniform_real_distribution<double> boundDistribution(0, 2);
+
+TEST(LinearInterpolationTest, HandlesNormalInputs) {
+    double x = valueDistribution(generator);
+    double x1 = x - boundDistribution(generator);
+    double x2 = x + boundDistribution(generator);
+
+    double yUnused = valueDistribution(generator);
+    double y1 = yUnused - boundDistribution(generator);
+    double y2 = yUnused + boundDistribution(generator);
+
+    // Linearly interpolate to solve for y
+    double y = y1 * (x2 - x) / (x2 - x1) + y2 * (x - x1) / (x2 - x1);
+
+    EXPECT_EQ(linearInterpolation(x1, x2, y1, y2, x), y);
+}