feat: pd_signal::interp()

google-tests/CMakeLists.txt

@@ -11,6 +11,7 @@ include_directories(${gtest_SOURCE_DIR}/include ${gtest_SOURCE_DIR} libnpy/inclu
 add_executable(Google_Tests_run
         test1.cpp
         test2.cpp
+        test3.cpp
 )
 
 file(COPY test1/data1.npy DESTINATION ${CMAKE_CURRENT_BINARY_DIR}/test1)

google-tests/test3.cpp

@@ -0,0 +1,27 @@
+//
+// Created by david on 04.03.2026.
+//
+#include <gtest/gtest.h>
+#include "pd_signal.h"
+
+using namespace pd_signal;
+
+TEST(SignalTest, interp_t1) {
+    //EXPECT_EQ();
+    std::vector<double> xp     { 1.0,      2.0,      4.0, 5.0, 5.01, 6.0 };
+    std::vector<double> fp     { 1.0,      2.0,      4.0, 5.0, 5.01, 7.0 };
+
+    std::vector<double> x { 0.9, 1.0, 1.5, 2.0, 3.9,    4.1, 5.0, 5.5, 6.0, 6.1 };
+    std::vector<double>y_e{ 1.0, 1.0, 1.5, 2.0, 3.9,    4.1, 5.0, 5.99494949495, 7.0, 7.0 };
+    size_t N = x.size();
+    // 5.99494949495 = (5.5-5.01)/0.99*(7-5.01)+5.01
+
+    std::vector<double> y;
+    interp(x, xp, fp, y);
+
+    // assert y == y_e, nb. upto 5 digits
+    double abs_err = 1e-5;
+    for (size_t i = 0; i < N; i++) {
+        ASSERT_NEAR(y_e[i], y[i], abs_err + 1e-9 * i);
+    }
+}