Merge pull request #26597 from jpreiss/quat_log

Public name for quaternion logarithm

.mailmap

@@ -718,6 +718,7 @@ Jaime R <38530589+Jaime02@users.noreply.github.com>
 Jaime Resano <gemailpersonal02@gmail.com>
 Jainul Vaghasia <jainulvaghasia@gmail.com> <jainulvaghasia@D-10-157-53-226.dhcp4.washington.edu>
 Jakub Wilk <jwilk@jwilk.net>
+James A. Preiss <jamesalanpreiss@gmail.com> jpreiss <jamesalanpreiss@gmail.com>
 James Abbatiello <abbeyj@gmail.com>
 James Aspnes <aspnes@cs.yale.edu>
 James Brandon Milam <jmilam343@gmail.com>

sympy/algebras/quaternion.py

@@ -972,22 +972,22 @@ def exp(self):
 
         return Quaternion(a, b, c, d)
 
-    def _ln(self):
-        """Returns the natural logarithm of the quaternion (_ln(q)).
+    def log(self):
+        r"""Returns the logarithm of the quaternion, given by $\log q$.
 
         Examples
         ========
 
         >>> from sympy import Quaternion
         >>> q = Quaternion(1, 2, 3, 4)
-        >>> q._ln()
+        >>> q.log()
         log(sqrt(30))
         + 2*sqrt(29)*acos(sqrt(30)/30)/29*i
         + 3*sqrt(29)*acos(sqrt(30)/30)/29*j
         + 4*sqrt(29)*acos(sqrt(30)/30)/29*k
 
         """
-        # _ln(q) = _ln||q|| + v/||v||*arccos(a/||q||)
+        # log(q) = log||q|| + v/||v||*arccos(a/||q||)
         q = self
         vector_norm = sqrt(q.b**2 + q.c**2 + q.d**2)
         q_norm = q.norm()

sympy/algebras/tests/test_quaternion.py

@@ -172,7 +172,7 @@ def test_quaternion_functions():
                2 * sqrt(29) * E * sin(sqrt(29)) / 29,
                3 * sqrt(29) * E * sin(sqrt(29)) / 29,
                4 * sqrt(29) * E * sin(sqrt(29)) / 29)
-    assert q1._ln() == \
+    assert q1.log() == \
     Quaternion(log(sqrt(30)),
                2 * sqrt(29) * acos(sqrt(30)/30) / 29,
                3 * sqrt(29) * acos(sqrt(30)/30) / 29,