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twinx / twiny inherit autoscale behavior for shared axis #7904

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Merged
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Jan 29, 2017
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twinx / twiny inherit autoscale behavior for shared axis #7904

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30 changes: 16 additions & 14 deletions lib/matplotlib/axes/_base.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3904,16 +3904,16 @@ def twinx(self):
"""
Create a twin Axes sharing the xaxis

Create a twin of Axes for generating a plot with a shared
x-axis but independent y-axis. The y-axis of self will have
ticks on left and the returned axes will have ticks on the
right. To ensure tick marks of both axis align, see
Create a new Axes instance with an invisible x-axis and an independent
y-axis positioned opposite to the original one (i.e. at right). The
x-axis autoscale setting will be inherited from the original Axes.
To ensure that the tick marks of both y-axes align, see
`~matplotlib.ticker.LinearLocator`

Returns
-------
Axis
The newly created axis
ax_twin : Axes
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wow, good catch!

The newly created Axes instance

Notes
-----
Expand All @@ -3924,6 +3924,7 @@ def twinx(self):
ax2.yaxis.tick_right()
ax2.yaxis.set_label_position('right')
ax2.yaxis.set_offset_position('right')
ax2.set_autoscalex_on(self.get_autoscalex_on())
self.yaxis.tick_left()
ax2.xaxis.set_visible(False)
ax2.patch.set_visible(False)
Expand All @@ -3933,25 +3934,26 @@ def twiny(self):
"""
Create a twin Axes sharing the yaxis

Create a twin of Axes for generating a plot with a shared
y-axis but independent x-axis. The x-axis of self will have
ticks on bottom and the returned axes will have ticks on the
top.
Create a new Axes instance with an invisible y-axis and an independent
x-axis positioned opposite to the original one (i.e. at top). The
y-axis autoscale setting will be inherited from the original Axes.
To ensure that the tick marks of both x-axes align, see
`~matplotlib.ticker.LinearLocator`
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I am not sure that I understand the last sentence. Specifically, how does looking at the documentation for LinearLocator ensure tick alignment? :)

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This is the original wording - do you have any suggestions for a better sentence? (or you could incorporate it in your PR since that deals with tickers)

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I will try to figure out what that sentence means exactly and attempt to improve it.


Returns
-------
Axis
The newly created axis
ax_twin : Axes
The newly created Axes instance

Notes
------
-----
For those who are 'picking' artists while using twiny, pick
events are only called for the artists in the top-most axes.
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top-most relative to what?

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I think this means the "original" Axes.

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Actually I'm not really familiar with the Artist/picker API, I'm not really sure what top-most is in this context..

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The Axes are rendered in some order (determined by the z-order and sorted in the Figure draw method). Which ever one draws last (has highest z-order) is the one that gets the pick event.

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If I remember correctly, the new axis ends up on top. I remember having some issues with legends getting obscured by gridlines because of this.

"""

ax2 = self._make_twin_axes(sharey=self)
ax2.xaxis.tick_top()
ax2.xaxis.set_label_position('top')
ax2.set_autoscaley_on(self.get_autoscaley_on())
self.xaxis.tick_bottom()
ax2.yaxis.set_visible(False)
ax2.patch.set_visible(False)
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Binary file added lib/matplotlib/tests/baseline_images/test_axes/twin_autoscale.png
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36 changes: 36 additions & 0 deletions lib/matplotlib/tests/test_axes.py
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Expand Up @@ -145,6 +145,42 @@ def test_twinx_cla():
assert ax.yaxis.get_visible()


@image_comparison(baseline_images=['twin_autoscale'], extensions=['png'])
def test_twinx_axis_scales():
x = np.array([0, 0.5, 1])
y = 0.5 * x
x2 = np.array([0, 1, 2])
y2 = 2 * x2

fig = plt.figure()
ax = fig.add_axes((0, 0, 1, 1), autoscalex_on=False, autoscaley_on=False)
ax.plot(x, y, color='blue', lw=10)

ax2 = plt.twinx(ax)
ax2.plot(x2, y2, 'r--', lw=5)

ax.margins(0, 0)
ax2.margins(0, 0)


@cleanup
def test_twin_inherit_autoscale_setting():
fig, ax = plt.subplots()
ax_x_on = ax.twinx()
ax.set_autoscalex_on(False)
ax_x_off = ax.twinx()

assert ax_x_on.get_autoscalex_on()
assert not ax_x_off.get_autoscalex_on()

ax_y_on = ax.twiny()
ax.set_autoscaley_on(False)
ax_y_off = ax.twiny()

assert ax_y_on.get_autoscaley_on()
assert not ax_y_off.get_autoscaley_on()


@image_comparison(baseline_images=["minorticks_on_rcParams_both"], extensions=['png'])
def test_minorticks_on_rcParams_both():
fig = plt.figure()
Expand Down