FIX: Use stable argsort

Author: effigies

nibabel/tests/test_parrec.py

@@ -173,8 +173,6 @@
 
 # DTI.PAR values for bvecs
 DTI_PAR_BVALS = [1000] * 6 + [0, 1000]
-# Numpy's argsort can be unstable so write indices manually
-DTI_PAR_BVALS_SORT_IDCS = [6, 0, 1, 2, 3, 4, 5, 7]
 
 EXAMPLE_IMAGES = [
     # Parameters come from load of Philips' conversion to NIfTI
@@ -526,7 +524,10 @@ def test_diffusion_parameters_strict_sort():
     # DTI_PAR_BVECS gives bvecs copied from first slice each vol in DTI.PAR
     # Permute to match bvec directions to acquisition directions
     # note that bval sorting occurs prior to bvec sorting
-    assert_almost_equal(bvecs, DTI_PAR_BVECS[np.ix_(DTI_PAR_BVALS_SORT_IDCS, [2, 0, 1])])
+    assert_almost_equal(
+        bvecs,
+        DTI_PAR_BVECS[np.ix_(np.argsort(DTI_PAR_BVALS, kind='stable'), [2, 0, 1])],
+    )
     # Check q vectors
     assert_almost_equal(dti_hdr.get_q_vectors(), bvals[:, None] * bvecs)
 

nibabel/tests/test_scripts.py

@@ -27,7 +27,7 @@
 from ..tmpdirs import InTemporaryDirectory
 from .nibabel_data import needs_nibabel_data
 from .scriptrunner import ScriptRunner
-from .test_parrec import DTI_PAR_BVALS, DTI_PAR_BVALS_SORT_IDCS, DTI_PAR_BVECS
+from .test_parrec import DTI_PAR_BVALS, DTI_PAR_BVECS
 from .test_parrec import EXAMPLE_IMAGES as PARREC_EXAMPLES
 from .test_parrec_data import AFF_OFF, BALLS
 
@@ -418,7 +418,7 @@ def test_parrec2nii_with_data():
         assert_almost_equal(np.loadtxt('DTI.bvals'), np.sort(DTI_PAR_BVALS))
         img = load('DTI.nii')
         data_sorted = img.get_fdata()
-        assert_almost_equal(data[..., DTI_PAR_BVALS_SORT_IDCS], data_sorted)
+        assert_almost_equal(data[..., np.argsort(DTI_PAR_BVALS, kind='stable')], data_sorted)
         del img
 
         # Writes .ordering.csv if requested