Add get_rows_per_scan utility and associated unit tests

CHANGELOG.md

@@ -5,7 +5,7 @@
 ### Changed
 
 - [[DAS-2216](https://bugs.earthdata.nasa.gov/browse/DAS-2216)]
-  The Swath Projector has been updated with quick fixes to add support for TEMPO level 2 data. These changes include optional transposing of arrays based on dimension sizes and updates to the configuration file for TEMPO_O3TOT_L2 to correctly locate coordinate variables and exclude science variables with dimensions that do no match those of the coordinate variables.
+  The Swath Projector has been updated with quick fixes to add support for TEMPO level 2 data. These changes include optional transposing of arrays based on dimension sizes, addition of rows_per_scan parameter for ewa interpolation, and updates to the configuration file for TEMPO_O3TOT_L2 to correctly locate coordinate variables and exclude science variables with dimensions that do no match those of the coordinate variables.
 
 ## [v1.1.1] - 2024-09-16
 

swath_projector/interpolation.py

@@ -25,6 +25,7 @@
 from swath_projector.utilities import (
     create_coordinates_key,
     get_coordinate_variable,
+    get_rows_per_scan,
     get_scale_and_offset,
     get_variable_file_path,
     get_variable_numeric_fill_value,
@@ -268,7 +269,7 @@ def get_ewa_results(
         ewa_information['target_area'],
         variable['values'],
         maximum_weight_mode=maximum_weight_mode,
-        rows_per_scan=2,  # Added in QuickFix DAS-2216 to be fixed in DAS-2220
+        rows_per_scan=get_rows_per_scan(variable['values'].shape[0]),
     )
 
     if variable['fill_value'] is not None:

swath_projector/utilities.py

@@ -246,3 +246,16 @@ def transpose_if_xdim_less_than_ydim(
         return np.ma.transpose(variable_values).copy()
 
     return variable_values
+
+
+def get_rows_per_scan(total_rows: int) -> int:
+    """
+    Finds the smallest divisor of the total number of rows. If no divisor is
+    found, return the total number of rows.
+    """
+    if total_rows < 2:
+        return 1
+    for row_number in range(2, int(total_rows**0.5) + 1):
+        if total_rows % row_number == 0:
+            return row_number
+    return total_rows

tests/unit/test_utilities.py

@@ -10,6 +10,7 @@
     construct_absolute_path,
     create_coordinates_key,
     get_coordinate_variable,
+    get_rows_per_scan,
     get_scale_and_offset,
     get_variable_file_path,
     get_variable_numeric_fill_value,
@@ -411,3 +412,17 @@ def test_masked_array(self):
         result = transpose_if_xdim_less_than_ydim(input_array)
         np.testing.assert_array_equal(result, expected_output)
         np.testing.assert_array_equal(result.mask, expected_output.mask)
+
+
+class TestGetRowsPerScan(TestCase):
+    def test_number_less_than_2(self):
+        self.assertEqual(get_rows_per_scan(1), 1)
+
+    def test_even_composite_number(self):
+        self.assertEqual(get_rows_per_scan(4), 2)
+
+    def test_odd_composite_number(self):
+        self.assertEqual(get_rows_per_scan(9), 3)
+
+    def test_prime_number(self):
+        self.assertEqual(get_rows_per_scan(3), 3)