Fix BayesQuasi when sample workspace has numeric axis

docs/source/release/v6.11.0/Inelastic/Bugfixes/37898.rst

@@ -0,0 +1 @@
+- Fixed an 'index out of range' error in the :ref:`BayesQuasi <algm-BayesQuasi>` algorithm when using a sample with a Numeric Axis.

scripts/Inelastic/IndirectCommon.py

@@ -169,13 +169,8 @@ def get_two_theta_and_q(workspace: Union[str, MatrixWorkspace]) -> Tuple[np.ndar
 
     # If axis is in Q need to calculate back to angles and just return axis values
     elif axis.isNumeric() and axis.getUnit().unitID() == "MomentumTransfer":
-        q_bin_edge = axis.extractValues()
-        q = list()
-        for i in range(1, len(q_bin_edge)):
-            q_centre = ((q_bin_edge[i] - q_bin_edge[i - 1]) / 2) + q_bin_edge[i - 1]
-            q.append(q_centre)
-        np_q = np.array(q)
-        two_theta = 2.0 * np.degrees(np.arcsin(np_q / k0))
+        q = axis.extractValues()
+        two_theta = 2.0 * np.degrees(np.arcsin(np.array(q) / k0))
 
     # Out of options here
     else:

scripts/test/IndirectCommonTests.py

@@ -9,7 +9,7 @@
 from os.path import join
 
 from mantid import config
-from mantid.api import AnalysisDataService
+from mantid.api import AnalysisDataService, NumericAxis
 from mantid.simpleapi import (
     AddSampleLog,
     CreateSampleWorkspace,
@@ -96,14 +96,31 @@ def test_get_two_theta_angles(self):
         actual_result = indirect_common.get_two_theta_angles(ws)
         self.assert_lists_almost_match(expected_result, actual_result)
 
-    def test_get_two_theta_and_q(self):
+    def test_get_two_theta_and_q_with_spectra_axis(self):
         ws = self.make_dummy_QENS_workspace()
         expected_theta_result = [29.700000000000006, 32.32, 34.949999999999996, 37.58, 40.209999999999994]
         expected_Q_result = [0.48372274526965625, 0.5253047207470042, 0.5667692111215948, 0.6079351677527525, 0.6487809073399485]
         actual_theta_result, actual_Q_result = indirect_common.get_two_theta_and_q(ws)
         self.assert_lists_almost_match(expected_theta_result, actual_theta_result)
         self.assert_lists_almost_match(expected_Q_result, actual_Q_result)
 
+    def test_get_two_theta_and_q_with_numeric_axis(self):
+        q_values = [0.48372274526965625, 0.5253047207470042, 0.5667692111215948, 0.6079351677527525, 0.6487809073399485]
+
+        ws = AnalysisDataService.retrieve(self.make_dummy_QENS_workspace())
+        numeric_axis = NumericAxis.create(len(q_values))
+        numeric_axis.setUnit("MomentumTransfer")
+        for i, q_value in enumerate(q_values):
+            numeric_axis.setValue(i, q_value)
+
+        ws.replaceAxis(1, numeric_axis)
+
+        actual_theta_values, actual_q_values = indirect_common.get_two_theta_and_q(ws)
+
+        expected_theta_values = [29.700000000000006, 32.32, 34.949999999999996, 37.58, 40.209999999999994]
+        self.assert_lists_almost_match(expected_theta_values, actual_theta_values)
+        self.assert_lists_almost_match(q_values, actual_q_values)
+
     def test_extract_float(self):
         data = "0.0 1 .2 3e-3 4.3 -5.5 6.0"
         expected_result = [0, 1, 0.2, 3e-3, 4.3, -5.5, 6.0]