def convertRefFrame(self, reframe2, reframe, epoch=None):
'''Convert this Cartesian point from one to an other reference frame.
@param reframe2: Reference frame to convert I{to} (L{RefFrame}).
@param reframe: Reference frame to convert I{from} (L{RefFrame}).
@keyword epoch: Optional epoch to observe for B{C{reframe}}, a
fractional calendar year (C{scalar}).
@return: The converted Cartesian point (C{Cartesian}) or
this Cartesian point if conversion is C{nil}.
@raise TRFError: No conversion available from
B{C{reframe}} to B{C{reframe2}}.
@raise TypeError: B{C{reframe2}} or B{C{reframe}} not a
L{RefFrame} or B{C{epoch}} not C{scalar}.
'''
_TypeError(RefFrame, reframe2=reframe2, reframe=reframe)
c = self
for t in _reframeTransforms(
reframe2, reframe,
reframe.epoch if epoch is None else _2epoch(epoch)):
c = c._applyHelmert(t, False)
return c
def epoch(self, epoch):
'''Set or clear this point's observed epoch.
@param epoch: Observed epoch, a fractional calendar year
(C{scalar}) or C{None}.
@raise TypeError: The B{C{epoch}} is not C{scalar}.
'''
self._epoch = None if epoch is None else _2epoch(epoch)