Fix ATAN2 calculation error. ATAT2(a,b)=ATAN(b/a)

tests/xlfunctions/test_math.py

@@ -41,6 +41,7 @@ def test_ATAN(self):
     def test_ARTAN2(self):
         self.assertAlmostEqual(math.ATAN2(1, 1), 0.785398163)
         self.assertAlmostEqual(math.ATAN2(-1, -1), -2.35619449)
+        self.assertAlmostEqual(math.ATAN2(1, 2), 1.10714872)
 
     def test_CEILING_number(self):
         self.assertEqual(math.CEILING(2.5, 1), 3)

tests/xlfunctions_vs_excel/atan2_test.py

@@ -28,3 +28,9 @@ def test_evaluation_A5(self):
             self.evaluator.evaluate('Sheet1!A5'),
             self.evaluator.get_cell_value('Sheet1!A5')
         )
+
+    def test_evaluation_A6(self):
+        self.assertEqual(
+            self.evaluator.evaluate('Sheet1!A6'),
+            self.evaluator.get_cell_value('Sheet1!A6')
+        )

xlcalculator/xlfunctions/math.py

@@ -111,7 +111,7 @@ def ATAN2(
     https://support.office.com/en-us/article/
         atan2-function-c04592ab-b9e3-4908-b428-c96b3a565033
     """
-    return np.arctan2(float(x_num), float(y_num))
+    return np.arctan2(float(y_num), float(x_num))
 
 
 @xl.register()