Bug fix: WX groupings PR miscalculating day length as number of files (…

…#2026)

* Adds missing brackets in calculation of start file and end file for middle of the day emphasis. This didn't matter for hourly inputs, which is what the unit tests focus upon. However, for 3-hourly data it is vital as otherwise the day length is not scaled by the interval to give a number of files from which to count back.

* Typo fix.

improver/wxcode/modal_code.py

@@ -512,10 +512,10 @@ def _emphasise_day_period(self, cube: Cube) -> Cube:
 
         n_times = len(day_cubes)
         start_file = np.clip(
-            (n_times - int(self.DAY_LENGTH - self.day_start / interval)), 0, None
+            (n_times - int((self.DAY_LENGTH - self.day_start) / interval)), 0, None
         )
         end_file = np.clip(
-            (n_times - int(self.DAY_LENGTH - self.day_end / interval)), 0, None
+            (n_times - int((self.DAY_LENGTH - self.day_end) / interval)), 0, None
         )
 
         for increment in range(1, self.day_weighting):

improver_tests/wxcode/wxcode/test_ModalFromGroupings.py

@@ -220,34 +220,34 @@ def test_expected_values_wet_bias(
 
 @pytest.mark.parametrize("record_run_attr", [False])
 @pytest.mark.parametrize("model_id_attr", [False, True])
-@pytest.mark.parametrize("interval", [1])
 @pytest.mark.parametrize("offset_reference_times", [False, True])
 @pytest.mark.parametrize("cube_type", ["gridded", "spot"])
 @pytest.mark.parametrize(
-    "data, day_weighting, day_start, day_end, day_length, expected",
+    "data, interval, day_weighting, day_start, day_end, day_length, expected",
     (
         # All weather codes supplied are considered as daytime.
         # There are more light shower codes, so this is the modal code.
-        ([1, 1, 1, 1, 10, 10, 10, 10, 10], 1, 0, 9, 24, 10),
+        ([1, 1, 1, 1, 10, 10, 10, 10, 10], 1, 1, 0, 9, 24, 10),
         # For a day length of 9 and a day weighting of 2, the number of clear day codes
         # doubles with one more shower symbol giving 6 dry codes, and 5 wet codes.
-        ([1, 1, 1, 1, 1, 10, 10, 10, 10], 2, 3, 5, 9, 1),
+        ([1, 1, 1, 1, 1, 10, 10, 10, 10], 1, 2, 3, 5, 9, 1),
         # Selecting a different period results in 6 dry codes and 6 wet codes,
         # so the resulting code is wet.
-        ([1, 1, 1, 1, 10, 10, 10, 10, 10], 2, 4, 7, 9, 10),
+        ([1, 1, 1, 1, 10, 10, 10, 10, 10], 1, 2, 4, 7, 9, 10),
         # A day weighting of 2 with a day length of 24 means that none of these codes
         # fall within the day period, and therefore the modal code is dry (1).
-        ([1, 1, 1, 1, 1, 10, 10, 10, 10], 2, 9, 15, 24, 1),
+        ([1, 1, 1, 1, 1, 10, 10, 10, 10], 1, 2, 9, 15, 24, 1),
         # A day weighting of 2 with a day length of 24 means that none of these codes
         # fall within the day period, and therefore the modal code is wet (10).
-        ([1, 1, 1, 1, 10, 10, 10, 10, 10], 2, 4, 7, 24, 10),
+        ([1, 1, 1, 1, 10, 10, 10, 10, 10], 1, 2, 4, 7, 24, 10),
         # Increasing the day weighting to 3 results in 8 dry codes and 7 wet codes, so
         # the resulting code is dry.
-        ([1, 1, 1, 1, 10, 10, 10, 10, 10], 3, 4, 7, 9, 1),
+        ([1, 1, 1, 1, 10, 10, 10, 10, 10], 1, 3, 4, 7, 9, 1),
         # An example for two points with the first point being dry, and the second point
         # being wetter, with day weighting resulting in a dry modal code.
         (
             [[1, 1, 1, 1, 1, 1, 1, 1, 1], [1, 1, 1, 1, 10, 10, 10, 10, 10]],
+            1,
             3,
             4,
             7,
@@ -258,12 +258,17 @@ def test_expected_values_wet_bias(
         # second point being wetter, with day weighting resulting in a dry modal code.
         (
             [[1, 1, 1, 1, 10, 1, 1, 1, 1], [1, 1, 1, 1, 10, 10, 10, 1, 1]],
+            1,
             3,
             2,
             5,
             9,
             [1, 10],
         ),
+        # More clear symbols, but partly cloudy symbol is emphasised more as it
+        # falls within the mid part of the day. Resulting symbol is partly cloudy.
+        # Uses 3-hourly data to ensure file counting works for non-hourly inputs.
+        ([12, 12, 10, 3, 3, 1, 0, 0], 3, 2, 6, 18, 24, 3),
     ),
 )
 def test_expected_values_day_weighting(