Merge pull request FABLE-3DXRD#568 from FABLE-3DXRD/unitcell-ring-tth

Add a method to unitcell to generate tth values for powder rings

Author: jonwright

ImageD11/indexing.py

@@ -461,6 +461,7 @@ def assigntorings(self):
             "Ring     (  h,  k,  l) Mult  total indexed to_index  ubis  peaks_per_ubi   tth  ds"
         )
         minpks = 0
+        tths = self.unitcell.ringtths(self.wavelength)
         # try reverse order instead
         for j in range(len(dsr))[::-1]:
             ind = np.compress(np.equal(self.ra, j), np.arange(self.ra.shape[0]))
@@ -479,7 +480,7 @@ def assigntorings(self):
             else:
                 expected_orients = "N/A"
                 expected_npks = "N/A"
-            tth = 2 * np.degrees(np.arcsin(dsr[j] * self.wavelength / 2))
+            tth = tths[j]
             logging.info(
                 "Ring %-3d (%3d,%3d,%3d)  %3d  %5d   %5d    %5d %5s     %2s  %.2f  %.2f"
                 % (

ImageD11/unitcell.py

@@ -270,6 +270,8 @@ def __init__(self, lattice_parameters, symmetry="P", verbose=0, name=None):
         self.limit = 0
 
         self.ringtol = 0.001
+        self.ringds = []  # a list of floats
+        self.ringhkls = {}  # a dict of lists of integer hkl
         # used for caching
         self.anglehkl_cache = {"ringtol": self.ringtol,
                                "B": self.B,
@@ -545,6 +547,19 @@ def makerings(self, limit, tol=0.001):
                 self.ringhkls[self.ringds[-1]] = [peak[1]]
         self.ringtol = tol
 
+    def ringtths(self, wavelength):
+        """
+        Computes the two theta values of powder rings, given a wavelength.
+        `makerings` must be called beforehand.
+        """
+        ring_ds = self.ringds
+        if len(ring_ds) == 0:
+            raise ValueError('No rings found. Call `makerings` before calling this function.')
+        tth = []
+        for ds in ring_ds:
+            tth.append(2 * np.degrees(np.arcsin(ds * wavelength / 2)))
+        return tth
+
     def anglehkls(self, h1, h2):
         """
         Compute the angle between reciprocal lattice vectors h1, h2