remove error msg, change copy method

Author: yucongalicechen

src/diffpy/utils/diffraction_objects.py

@@ -388,11 +388,9 @@ def scale_to(self, target_diff_object, q=None, tth=None, d=None, offset=0):
         -------
         the rescaled DiffractionObject as a new object
         """
-        scaled = deepcopy(self)
+        scaled = self.copy()
         xtype = "q" if q is not None else "tth" if tth is not None else "d" if d is not None else "q"
         data, target = self.on_xtype(xtype), target_diff_object.on_xtype(xtype)
-        if len(data[0]) == 0 or len(target[0]) == 0:
-            raise ValueError("I cannot scale diffraction objects with empty arrays.")
 
         xvalue = q if xtype == "q" else tth if xtype == "tth" else d
         if xvalue is None:

tests/test_diffraction_objects.py

@@ -331,21 +331,6 @@ def test_scale_to(inputs, expected):
     assert np.allclose(scaled_diff_object.on_xtype(expected[0])[1], expected[1])
 
 
-def test_scale_to_bad():
-    # UC1: at least one of the y-arrays is empty
-    orig_diff_object = DiffractionObject(
-        xarray=np.array([]), yarray=np.array([]), xtype="tth", wavelength=2 * np.pi
-    )
-    target_diff_object = DiffractionObject(
-        xarray=np.array([11, 14, 16, 20, 25, 30]),
-        yarray=np.array([2, 3, 4, 5, 6, 7]),
-        xtype="tth",
-        wavelength=2 * np.pi,
-    )
-    with pytest.raises(ValueError, match="I cannot scale diffraction objects with empty arrays."):
-        orig_diff_object.scale_to(target_diff_object, tth=20)
-
-
 params_index = [
     # UC1: exact match
     ([4 * np.pi, np.array([30.005, 60]), np.array([1, 2]), "tth", "tth", 30.005], [0]),