low freq filter

tests/test_processing.py

@@ -7,6 +7,7 @@ import unittest
 
 from rfg_adc_plotter.constants import C_M_S, FFT_LEN, SWEEP_FREQ_MAX_GHZ, SWEEP_FREQ_MIN_GHZ
 from rfg_adc_plotter.gui.pyqtgraph_backend import (
+    apply_distance_cut_to_axis,
     apply_working_range,
     apply_working_range_to_aux_curves,
     build_main_window_layout,
@@ -16,6 +17,7 @@ from rfg_adc_plotter.gui.pyqtgraph_backend import (
     resolve_axis_bounds,
     resolve_heavy_refresh_stride,
     resolve_initial_window_size,
+    resolve_distance_cut_start,
     sanitize_curve_data_for_display,
     sanitize_image_for_display,
     set_image_rect_if_ready,
@@ -317,6 +319,22 @@ class ProcessingTests(unittest.TestCase):
 
         self.assertIsNone(bounds)
 
+    def test_resolve_distance_cut_start_interpolates_with_percent(self):
+        axis = np.asarray([0.0, 1.0, 2.0, 3.0], dtype=np.float64)
+        cut_start = resolve_distance_cut_start(axis, 50.0)
+
+        self.assertIsNotNone(cut_start)
+        self.assertAlmostEqual(float(cut_start), 1.5, places=6)
+
+    def test_apply_distance_cut_to_axis_keeps_farthest_point_for_extreme_cut(self):
+        axis = np.asarray([0.0, 1.0, 2.0, 3.0], dtype=np.float64)
+        cut_axis, keep_mask = apply_distance_cut_to_axis(axis, 10.0)
+
+        self.assertEqual(cut_axis.shape, (1,))
+        self.assertEqual(keep_mask.shape, axis.shape)
+        self.assertTrue(bool(keep_mask[-1]))
+        self.assertAlmostEqual(float(cut_axis[0]), 3.0, places=6)
+
     def test_resolve_initial_window_size_stays_within_small_screen(self):
         width, height = resolve_initial_window_size(800, 480)