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Improve(?) implementation of secondary_axis. #14463

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13 changes: 4 additions & 9 deletions examples/axisartist/demo_axisline_style.py
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Original file line number Diff line number Diff line change
Expand Up @@ -11,24 +11,19 @@
example.
"""

from mpl_toolkits.axisartist.axislines import SubplotZero
from mpl_toolkits.axisartist.axislines import Subplot
import matplotlib.pyplot as plt
import numpy as np


fig = plt.figure()
ax = SubplotZero(fig, 111)
ax = Subplot(fig, 111)
fig.add_subplot(ax)

for direction in ["xzero", "yzero"]:
# adds arrows at the ends of each axis
for direction in ["bottom", "left"]: # Add arrows for bottom and left axes.
ax.axis[direction].set_axisline_style("-|>")

# adds X and Y-axis from the origin
ax.axis[direction].set_visible(True)

for direction in ["left", "right", "bottom", "top"]:
# hides borders
for direction in ["top", "right"]: # Hide top and right axes.
ax.axis[direction].set_visible(False)

x = np.linspace(-0.5, 1., 100)
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9 changes: 6 additions & 3 deletions examples/axisartist/simple_axisartist1.py
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@@ -1,9 +1,12 @@
"""
==================
Simple Axisartist1
==================
========================================
Using axisartist to place an axis at y=0
========================================

Note that the following example can also be implemented without mpl_toolkits;
see :doc:`/gallery/ticks_and_spines/spine_placement_demo`.
"""

import matplotlib.pyplot as plt
from mpl_toolkits import axisartist

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21 changes: 21 additions & 0 deletions examples/axisartist/simple_axisline.py
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Expand Up @@ -34,4 +34,25 @@
ax.axis["right2"].label.set_text("Label Y2")

ax.plot([-2, 3, 2])

###############################################################################
# Or, without axisartist, one can use secondary axes to add the additional
# axes:

fig, ax = plt.subplots()
fig.subplots_adjust(right=0.85)

ax.spines["top"].set_visible(False)
ax.spines["right"].set_visible(False)

ax1 = ax.secondary_xaxis(0)
ax1.spines["bottom"].set_position(("data", 0))
ax1.set_xlabel("Axis Zero")

ax2 = ax.secondary_yaxis(1)
ax2.spines["right"].set_position(("outward", 20))
ax2.set_ylabel("Label Y2")

ax.plot([-2, 3, 2])

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OK, this is nice. Can this be added as an example in the main spines section as well? Or moved there, with a link to it here? Putting this second in this section makes it look like this is a deprecated way to do it, whereas I think the goal is for it to be the canonical way.

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I removed the additions to simple_axisline2 and simple_axisartist1 and just linked them https://matplotlib.org/devdocs/gallery/ticks_and_spines/spine_placement_demo.html#sphx-glr-gallery-ticks-and-spines-spine-placement-demo-py instead.

I think I'll leave the multi-axes example as it is right now because there's no completely equivalent example elsewhere and I don't want to bother about proper explanations for now, but we can always move it there later (e.g. when we kill SubplotZero...).

plt.show()
11 changes: 7 additions & 4 deletions examples/axisartist/simple_axisline2.py
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Original file line number Diff line number Diff line change
@@ -1,14 +1,17 @@
"""
================
Simple Axisline2
================
===================
SubplotZero example
===================

Note that the following example can also be implemented without mpl_toolkits;
see :doc:`/gallery/ticks_and_spines/spine_placement_demo`.
"""

import matplotlib.pyplot as plt
from mpl_toolkits.axisartist.axislines import SubplotZero
import numpy as np

fig = plt.figure(figsize=(4, 3))
fig = plt.figure()

# a subplot with two additional axis, "xzero" and "yzero". "xzero" is
# y=0 line, and "yzero" is x=0 line.
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28 changes: 10 additions & 18 deletions lib/matplotlib/axes/_secondary_axes.py
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Expand Up @@ -40,6 +40,10 @@ def __init__(self, parent, orientation, location, functions, **kwargs):
self._layoutbox = None
self._poslayoutbox = None

# Make this axes always follow the parent axes' position.
self.set_axes_locator(
_axes._InsetLocator([0, 0, 1, 1], self._parent.transAxes))

self.set_location(location)
self.set_functions(functions)

Expand All @@ -52,6 +56,7 @@ def __init__(self, parent, orientation, location, functions, **kwargs):
otheraxis.set_major_locator(mticker.NullLocator())
otheraxis.set_ticks_position('none')

self.patch.set_visible(False)
for st in self._otherstrings:
self.spines[st].set_visible(False)
for st in self._locstrings:
Expand Down Expand Up @@ -95,8 +100,7 @@ def set_location(self, location):
parent axes to put the new axes, 0.0 being the bottom (or left)
and 1.0 being the top (or right).
"""

# This puts the rectangle into figure-relative coordinates.
# Put the spine into axes-relative coordinates.
if isinstance(location, str):
if location in ['top', 'right']:
self._pos = 1.
Expand All @@ -108,22 +112,8 @@ def set_location(self, location):
f"{self._locstrings[1]!r}, or a float, not {location!r}")
else:
self._pos = location
self._loc = location

if self._orientation == 'x':
# An x-secondary axes is like an inset axes from x = 0 to x = 1 and
# from y = pos to y = pos + eps, in the parent's transAxes coords.
bounds = [0, self._pos, 1., 1e-10]
else:
bounds = [self._pos, 0, 1e-10, 1]

secondary_locator = _axes._InsetLocator(bounds, self._parent.transAxes)

# this locator lets the axes move in the parent axes coordinates.
# so it never needs to know where the parent is explicitly in
# figure coordinates.
# it gets called in `ax.apply_aspect() (of all places)
self.set_axes_locator(secondary_locator)
for loc in self._locstrings:
self.spines[loc].set_position(('axes', self._pos))

def apply_aspect(self, position=None):
# docstring inherited.
Expand Down Expand Up @@ -235,9 +225,11 @@ def _set_lims(self):
if self._orientation == 'x':
lims = self._parent.get_xlim()
set_lim = self.set_xlim
self.set_ylim(self._parent.get_ylim())
if self._orientation == 'y':
lims = self._parent.get_ylim()
set_lim = self.set_ylim
self.set_xlim(self._parent.get_xlim())
order = lims[0] < lims[1]
lims = self._functions[0](np.array(lims))
neworder = lims[0] < lims[1]
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