Expose numeric trend segment formulas from native reconstruction models

python/tests/test_plot_formula.py

@@ -0,0 +1,32 @@
+"""Formula coefficients must reproduce the native reconstruction, not a refit."""
+import unittest
+from set_devices.signal_reconstruction import reconstruct
+from set_devices.plot_formula import linear_piece
+
+
+class PlotFormulaTests(unittest.TestCase):
+    def test_all_methods_match_native_values_on_irregular_and_duplicate_knots(self):
+        points = [(0, 2), (.3, 8), (.3, 4), (1.1, -3), (2, 7), (4, 1), (5, 2)]
+        for method in ('linear', 'pchip', 'spline', 'polynomial'):
+            result = reconstruct(points, method, 101, 3, with_model=True)
+            for x, y in result.points:
+                piece = next(piece for piece in result.pieces if piece.left <= x <= piece.right)
+                self.assertAlmostEqual(y, piece.value(x), places=9)
+
+    def test_polynomial_model_with_fewer_output_samples_than_coefficients(self):
+        points = [(i, 1 + i * .2 - i ** 2 * .03 + i ** 5 * .0001) for i in range(9)]
+        result = reconstruct(points, 'polynomial', 2, 5, with_model=True)
+        for x, y in points:
+            self.assertAlmostEqual(y, result.pieces[0].value(x), places=9)
+
+    def test_source_line_and_formula_use_displayed_origin(self):
+        piece = linear_piece([1000, 1100, 1200], [1, 3, 0], 1050)
+        self.assertAlmostEqual(2, piece.value(1050))
+        text = piece.text(1000, 'мс')
+        self.assertIn('y = 1 +2·u', text)
+        self.assertIn('0 ≤ x ≤ 100 мс', text)
+        self.assertIsNone(linear_piece([0, 1, 2], [1, float('nan'), 3], .5))
+
+
+if __name__ == '__main__':
+    unittest.main()