change methods se2 and se3 to skewa

Author: petercorke

spatialmath/twist.py

@@ -825,23 +825,24 @@ def Ad(self):
 
 
 
-    def se3(self):
+    def skewa(self):
         """
         Convert 3D twist to se(3)
 
         :return: An se(3) matrix
         :rtype: ndarray(4,4)
 
-        ``X.se3()`` is the twist as an se(3) matrix, which is an augmented
-        skew-symmetric 4x4 matrix.
+        ``X.skewa()`` is the twist as a 4x4 augmented skew-symmetric matrix
+        belonging to the group se(3). This is the Lie algebra of the
+        corresponding SE(3) element. 
 
         Example:
         
         .. runblock:: pycon
 
             >>> from spatialmath import Twist3, base
             >>> S = Twist3.Rx(0.3)
-            >>> se = S.se3()
+            >>> se = S.skewa()
             >>> se
             >>> base.trexp(se)
         """
@@ -1436,23 +1437,24 @@ def SE2(self, theta=1, unit='rad'):
         else:
             return SE2([base.trexp2(self.S * t) for t in theta])
 
-    def se2(self):
+    def skewa(self):
         """
         Convert 2D twist to se(2)
 
         :return: An se(2) matrix
         :rtype: ndarray(3,3)
 
-        ``X.se2()`` is the twist as an se(2) matrix, which is an augmented
-        skew-symmetric 3x3 matrix.
+        ``X.skewa()`` is the twist as a 3x3 augmented skew-symmetric matrix
+        belonging to the group se(2). This is the Lie algebra of the
+        corresponding SE(2) element. 
 
         Example:
         
         .. runblock:: pycon
 
             >>> from spatialmath import Twist2, base
             >>> S = Twist2([1,2,3])
-            >>> se = S.se2()
+            >>> se = S.skewa()
             >>> se
             >>> base.trexp2(se)
         """

tests/test_twist.py

@@ -73,7 +73,7 @@ def test_conversion_se3(self):
         s = [1, 2, 3, 4, 5, 6]
         x = Twist3(s)
 
-        array_compare(x.se3(), np.array([[ 0., -6.,  5.,  1.],
+        array_compare(x.skewa(), np.array([[ 0., -6.,  5.,  1.],
                     [ 6.,  0., -4.,  2.],
                     [-5.,  4.,  0.,  3.],
                     [ 0.,  0.,  0.,  0.]]))
@@ -88,7 +88,7 @@ def test_list_constuctor(self):
         self.assertIsInstance(a, Twist3)
         self.assertEqual(len(a), 4)
 
-        a = Twist3([x.se3(), x.se3(), x.se3(), x.se3()])
+        a = Twist3([x.skewa(), x.skewa(), x.skewa(), x.skewa()])
         self.assertIsInstance(a, Twist3)
         self.assertEqual(len(a), 4)
 
@@ -109,7 +109,7 @@ def test_predicate(self):
         x = Twist3.UnitPrismatic([1, 2, 3])
         self.assertTrue(x.isprismatic)
 
-        self.assertTrue(Twist3.isvalid(x.se3()))
+        self.assertTrue(Twist3.isvalid(x.skewa()))
         self.assertTrue(Twist3.isvalid(x.S))
 
         self.assertFalse(Twist3.isvalid(2))
@@ -257,7 +257,7 @@ def test_conversion_se2(self):
         s = [1, 2, 3]
         x = Twist2(s)
 
-        array_compare(x.se2(), np.array([[ 0., -3.,  1.],
+        array_compare(x.skewa(), np.array([[ 0., -3.,  1.],
                                        [ 3.,  0.,  2.],
                                        [ 0.,  0.,  0.]]))
 
@@ -268,7 +268,7 @@ def test_list_constuctor(self):
         self.assertIsInstance(a, Twist2)
         self.assertEqual(len(a), 4)
 
-        a = Twist2([x.se2(), x.se2(), x.se2(), x.se2()])
+        a = Twist2([x.skewa(), x.skewa(), x.skewa(), x.skewa()])
         self.assertIsInstance(a, Twist2)
         self.assertEqual(len(a), 4)
 
@@ -289,7 +289,7 @@ def test_predicate(self):
         x = Twist2.UnitPrismatic([1, 2])
         self.assertTrue(x.isprismatic)
 
-        self.assertTrue(Twist2.isvalid(x.se2()))
+        self.assertTrue(Twist2.isvalid(x.skewa()))
         self.assertTrue(Twist2.isvalid(x.S))
 
         self.assertFalse(Twist2.isvalid(2))