raise valueerror for tth>180, arcsin value > 1

Author: yucongalicechen

src/diffpy/utils/scattering_objects/diffraction_objects.py

@@ -323,9 +323,11 @@ def q_to_tth(self):
         q = np.asarray(q)
         wavelength = float(self.wavelength)
         pre_factor = wavelength / (4 * np.pi)
-        # limit q * pre_factor to 1 to avoid invalid input to arcsin
-        arcsin_value = np.where(q * pre_factor <= 1, q * pre_factor, 1)
-        return np.rad2deg(2.0 * np.arcsin(arcsin_value))
+        if np.any(np.abs(q * pre_factor) > 1):
+            raise ValueError(
+                "Invalid input for arcsin: some values exceed the range [-1, 1]. " "Check wavelength or q values."
+            )
+        return np.rad2deg(2.0 * np.arcsin(q * pre_factor))
 
     def tth_to_q(self):
         r"""
@@ -362,6 +364,8 @@ def tth_to_q(self):
             of ``wavelength``
         """
         two_theta = np.asarray(np.deg2rad(self.on_tth[0]))
+        if np.any(two_theta > np.pi):
+            raise ValueError("Two theta exceeds 180 degrees.")
         wavelength = float(self.wavelength)
         pre_factor = (4 * np.pi) / wavelength
         return pre_factor * np.sin(two_theta / 2)
@@ -425,6 +429,8 @@ def tth_to_d(self):
             of ``wavelength``
         """
         two_theta = np.asarray(np.deg2rad(self.on_tth[0]))
+        if np.any(two_theta > np.pi):
+            raise ValueError("Two theta exceeds 180 degrees.")
         wavelength = float(self.wavelength)
         sin_two_theta = np.sin(two_theta / 2)
         d = np.where(sin_two_theta != 0, wavelength / (2 * sin_two_theta), np.inf)
@@ -452,7 +458,11 @@ def d_to_tth(self):
         """
         d = np.asarray(self.on_d[0])
         wavelength = float(self.wavelength)
-        pre_factor = np.where(d != 0, wavelength / (2 * d), 1)
+        pre_factor = wavelength / (2 * d)
+        if np.any(np.abs(pre_factor) > 1):
+            raise ValueError(
+                "Invalid input for arcsin: some values exceed the range [-1, 1]. " "Check wavelength or d values."
+            )
         return np.rad2deg(2.0 * np.arcsin(pre_factor))[::-1]
 
     def set_all_arrays(self):

tests/test_diffraction_objects.py

@@ -232,25 +232,40 @@ def test_diffraction_objects_equality(inputs1, inputs2, expected):
 
 
 def test_q_to_tth():
+    # valid q values including edge cases when q=0 or 1, expected tth values are 2 * arcsin(q)
     actual = Diffraction_object(wavelength=4 * np.pi)
-    setattr(actual, "on_q", [[0, 0.2, 0.4, 0.6, 0.8, 1, 40, 60], [1, 2, 3, 4, 5, 6, 7, 8]])
+    setattr(actual, "on_q", [[0, 0.2, 0.4, 0.6, 0.8, 1], [1, 2, 3, 4, 5, 6]])
     actual_tth = actual.q_to_tth()
-    # expected tth values are 2 * arcsin(q)
-    # when q gets large, we set tth = 180
-    # we allow q to exceed QMAX for user inputs
-    expected_tth = [0, 23.07392, 47.15636, 73.73980, 106.26020, 180, 180, 180]
+    expected_tth = [0, 23.07392, 47.15636, 73.73980, 106.26020, 180]
     assert np.allclose(actual_tth, expected_tth)
 
 
+def test_q_to_tth_bad():
+    # invalid q values when arcsin value is not in the range of [-1, 1]
+    actual = Diffraction_object(wavelength=4 * np.pi)
+    setattr(actual, "on_q", [[0.6, 0.8, 1, 1.2], [1, 2, 3, 4]])
+    with pytest.raises(ValueError):
+        actual.q_to_tth()
+
+
 def test_tth_to_q():
+    # valid tth values including edge cases when tth=0 or 180 degree,
+    # expected q vales are sin15, sin30, sin45, sin60, sin90
     actual = Diffraction_object(wavelength=4 * np.pi)
     setattr(actual, "on_tth", [[0, 30, 60, 90, 120, 180], [1, 2, 3, 4, 5, 6]])
     actual_q = actual.tth_to_q()
-    # expected q vales are sin15, sin30, sin45, sin60, sin90
     expected_q = [0, 0.258819, 0.5, 0.707107, 0.866025, 1]
     assert np.allclose(actual_q, expected_q)
 
 
+def test_tth_to_q_bad():
+    # invalid tth values > 180 degree
+    actual = Diffraction_object(wavelength=4 * np.pi)
+    setattr(actual, "on_tth", [[0, 30, 60, 90, 120, 181], [1, 2, 3, 4, 5, 6]])
+    with pytest.raises(ValueError):
+        actual.tth_to_q()
+
+
 def test_q_to_d():
     actual = Diffraction_object()
     setattr(actual, "on_q", [[0, np.pi, 2 * np.pi, 3 * np.pi, 4 * np.pi, 5 * np.pi], [1, 2, 3, 4, 5, 6]])
@@ -270,14 +285,23 @@ def test_d_to_q():
 
 
 def test_tth_to_d():
+    # valid tth values including edge cases when tth=0 or 180 degree,
+    # expected d values are DMAX=100, 1/sin15, 1/sin30, 1/sin45, 1/sin60, 1/sin90, in reverse order
     actual = Diffraction_object(wavelength=2)
     setattr(actual, "on_tth", [[0, 30, 60, 90, 120, 180], [1, 2, 3, 4, 5, 6]])
     actual_d = actual.tth_to_d()
-    # expected d values are DMAX=100, 1/sin15, 1/sin30, 1/sin45, 1/sin60, 1/sin90, in reverse order
     expected_d = [1, 1.1547, 1.41421, 2, 3.8637, 100]
     assert np.allclose(actual_d, expected_d)
 
 
+def test_tth_to_d_bad():
+    # invalid tth values > 180 degree
+    actual = Diffraction_object(wavelength=2)
+    setattr(actual, "on_tth", [[0, 30, 60, 90, 120, 181], [1, 2, 3, 4, 5, 6]])
+    with pytest.raises(ValueError):
+        actual.tth_to_d()
+
+
 def test_d_to_tth():
     actual = Diffraction_object(wavelength=2)
     setattr(actual, "on_d", [[0, 2, 4, 6, 8, 100, 200], [1, 2, 3, 4, 5, 6, 7]])
@@ -289,6 +313,15 @@ def test_d_to_tth():
     assert np.allclose(actual_tth, expected_tth)
 
 
+def test_d_to_tth_bad():
+    # invalid d values when arcsin value is not in the range of [-1, 1]
+    actual = Diffraction_object(wavelength=2)
+    setattr(actual, "on_d", [[0, 10, 20, 30], [1, 2, 3, 4]])
+    with pytest.raises(ValueError):
+        actual.d_to_tth()
+
+
+# Inputs cover a good valid range and provide the same expected values, ensuring conversion precision.
 params_array = [
     (["tth", "on_tth", [30, 60, 90, 120, 150], [1, 2, 3, 4, 5]]),
     (["q", "on_q", [1.626208, 3.141593, 4.442883, 5.441398, 6.069091], [1, 2, 3, 4, 5]]),