docs(ets): add fixjoint examples and version markers

src/roboticstoolbox/ets/ETS.py

@@ -166,6 +166,23 @@ def fixjoint(self, j: int, value: float, unit: str = "rad") -> ETS:
         :param unit: angular unit for rotational joints, "rad" [default] or "deg"
         :returns: ETS with one fewer joint
         :raises ValueError: for an invalid joint position or angular unit
+
+        A flipped joint can be fixed in degrees, without modifying the original
+        sequence. This also works on the kinematics of a robot:
+
+        .. runblock:: pycon
+
+            >>> from roboticstoolbox import ET, models
+            >>> ets = ET.Rz(flip=True) * ET.tx(1) * ET.Ry()
+            >>> fixed = ets.fixjoint(0, 90, unit="deg")
+            >>> fixed.n, ets.n
+            (1, 2)
+            >>> robot = models.ETS.Panda()
+            >>> reduced = robot.ets().fixjoint(2, 0)
+            >>> reduced.n == robot.n - 1
+            True
+
+        .. versionadded:: 1.5.0
         """
         # bool subclasses int, but must not select joint 0 or 1.
         if (

src/roboticstoolbox/ets/ETS2.py

@@ -147,6 +147,18 @@ def fixjoint(self, j: int, value: float, unit: str = "rad") -> ETS2:
         :param unit: angular unit for rotational joints, "rad" [default] or "deg"
         :returns: ETS2 with one fewer joint
         :raises ValueError: for an invalid joint position or angular unit
+
+        Fixing a flipped revolute joint preserves the other joint as a variable:
+
+        .. runblock:: pycon
+
+            >>> from roboticstoolbox import ET2
+            >>> ets = ET2.R(flip=True) * ET2.tx(1) * ET2.R()
+            >>> fixed = ets.fixjoint(0, 90, unit="deg")
+            >>> fixed.n, ets.n
+            (1, 2)
+
+        .. versionadded:: 1.5.0
         """
         # bool subclasses int, but must not select joint 0 or 1.
         if (