Add is_polar() utility for classifying polar space groups

reciprocalspaceship/utils/__init__.py

@@ -42,5 +42,5 @@
     is_centric,
     to_structurefactor,
 )
-from reciprocalspaceship.utils.symop import apply_to_hkl, phase_shift
+from reciprocalspaceship.utils.symmetry import apply_to_hkl, is_polar, phase_shift
 from reciprocalspaceship.utils.units import angstroms2ev, ev2angstroms

reciprocalspaceship/utils/asu.py

@@ -4,7 +4,7 @@
 from reciprocalspaceship.decorators import cellify, spacegroupify
 from reciprocalspaceship.utils.cell import generate_reciprocal_cell
 from reciprocalspaceship.utils.structurefactors import is_absent, is_centric
-from reciprocalspaceship.utils.symop import apply_to_hkl, phase_shift
+from reciprocalspaceship.utils.symmetry import apply_to_hkl, phase_shift
 
 # fmt: off
 ccp4_hkl_asu = [

reciprocalspaceship/utils/phases.py

@@ -40,7 +40,7 @@ def get_phase_restrictions(H, spacegroup):
          list is returned for Miller indices without phase restrictions
     """
     from reciprocalspaceship.utils.asu import is_absent, is_centric
-    from reciprocalspaceship.utils.symop import apply_to_hkl, phase_shift
+    from reciprocalspaceship.utils.symmetry import apply_to_hkl, phase_shift
 
     friedel_op = gemmi.Op("-x,-y,-z")
     # Grabs all the non-identity symops

reciprocalspaceship/utils/symop.py → reciprocalspaceship/utils/symmetry.py

@@ -1,5 +1,7 @@
 import numpy as np
 
+from reciprocalspaceship.decorators import spacegroupify
+
 
 def apply_to_hkl(H, op):
     """
@@ -56,3 +58,23 @@ def phase_shift(H, op):
         array of phase shifts
     """
     return -2 * np.pi * np.matmul(H, op.tran) / op.DEN
+
+
+@spacegroupify
+def is_polar(spacegroup):
+    """
+    Classify whether spacegroup is polar
+
+    Parameters
+    ----------
+    spacegroup : str, int, gemmi.SpaceGroup
+        Spacegroup to classify as polar
+
+    Returns
+    -------
+    bool
+        Whether the spacegroup is polar
+    """
+    sym_ops = spacegroup.operations().sym_ops
+    a = np.array([op.rot for op in sym_ops])
+    return ~(a < 0).any(axis=1).any(axis=0).all()

tests/data/gen_sgtbx_is_polar.py

@@ -0,0 +1,21 @@
+"""
+Generate test data using sgtbx classifications of polar spacegroups
+"""
+
+import pandas as pd
+from cctbx import sgtbx
+
+# Classify all space group settings
+is_polar = []
+xhms = []
+for sg in sgtbx.space_group_symbol_iterator():
+    sgtbx_polar = (
+        sgtbx.space_group(sg).info().number_of_continuous_allowed_origin_shifts() > 0
+    )
+    xhm = sg.universal_hermann_mauguin()
+    is_polar.append(sgtbx_polar)
+    xhms.append(xhm)
+
+# Write out CSV
+df = pd.DataFrame({"xhm": xhms, "is_polar": is_polar})
+df.to_csv("sgtbx/sgtbx_polar.csv", index=None)