from matplotlib import pyplot as plt
def twin(show="xy", ax=None):
"""
Call signature::
ax = twin()
create a twin of Axes for generating a plot with a shared
x-axis and y-axis.
The x-axis (y-axis) of ax will have ticks on bottom (left)
and the returned axes will have ticks on the top (right).
.. note::
For those who are 'picking' artists while using twin, pick
events are only called for the artists in the top-most axes.
This function will be wrong when the axis-limits are changed by xticks.
This can be corrected by call `xlim` to reset the limits.
"""
assert show in ['x', 'y', 'xy']
if ax is None:
ax = plt.gca()
ax.xaxis.tick_bottom()
ax.yaxis.tick_left()
ax2 = ax._make_twin_axes()
ax2._shared_x_axes.join(ax2, ax)
ax2._shared_y_axes.join(ax2, ax)
ax2._adjustable = 'datalim'
ax2.set_xlim(ax.get_xlim(), emit=False, auto=False)
ax2.set_ylim(ax.get_ylim(), emit=False, auto=False)
ax2.xaxis._set_scale(ax.xaxis.get_scale())
ax2.yaxis._set_scale(ax.yaxis.get_scale())
ax2.xaxis.tick_top()
ax2.yaxis.tick_right()
ax2.xaxis.set_label_position('top')
ax2.yaxis.set_label_position('right')
ax2.yaxis.set_offset_position('right')
ax2.patch.set_visible(False)
if show == 'x':
ax2.yaxis.set_visible(False)
elif show == 'y':
ax2.xaxis.set_visible(False)
return ax2