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Oct 16, 2021
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Demonstrate inset_axes in scatter_hist example. #21283

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12 changes: 6 additions & 6 deletions examples/axes_grid1/scatter_hist_locatable_axes.py
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Expand Up @@ -3,16 +3,16 @@
Scatter Histogram (Locatable Axes)
==================================

Show the marginal distributions of a scatter as histograms at the sides of
Show the marginal distributions of a scatter plot as histograms at the sides of
the plot.

For a nice alignment of the main axes with the marginals, the axes positions
are defined by a ``Divider``, produced via `.make_axes_locatable`.
are defined by a ``Divider``, produced via `.make_axes_locatable`. Note that
the ``Divider`` API allows setting axes sizes and pads in inches, which is its
main feature.

An alternative method to produce a similar figure is shown in the
:doc:`/gallery/lines_bars_and_markers/scatter_hist` example. The advantage of
the locatable axes method shown below is that the marginal axes follow the
fixed aspect ratio of the main axes.
If one wants to set axes sizes and pads relative to the main Figure, see the
:doc:`/gallery/lines_bars_and_markers/scatter_hist` example.
"""

import numpy as np
Expand Down
99 changes: 48 additions & 51 deletions examples/lines_bars_and_markers/scatter_hist.py
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Expand Up @@ -3,18 +3,22 @@
Scatter plot with histograms
============================

Show the marginal distributions of a scatter as histograms at the sides of
Show the marginal distributions of a scatter plot as histograms at the sides of
the plot.

For a nice alignment of the main axes with the marginals, two options are shown
below.
below:

* the axes positions are defined in terms of rectangles in figure coordinates
* the axes positions are defined via a gridspec
.. contents::
:local:

While `.Axes.inset_axes` may be a bit more complex, it allows correct handling
of main axes with a fixed aspect ratio.

An alternative method to produce a similar figure using the ``axes_grid1``
toolkit is shown in the
:doc:`/gallery/axes_grid1/scatter_hist_locatable_axes` example.
toolkit is shown in the :doc:`/gallery/axes_grid1/scatter_hist_locatable_axes`
example. Finally, it is also possible to position all axes in absolute
coordinates using `.Figure.add_axes` (not shown here).

Let us first define a function that takes x and y data as input, as well
as three axes, the main axes for the scatter, and two marginal axes. It will
Expand Down Expand Up @@ -52,60 +56,53 @@ def scatter_hist(x, y, ax, ax_histx, ax_histy):

#############################################################################
#
# Axes in figure coordinates
# --------------------------
#
# To define the axes positions, `.Figure.add_axes` is provided with a rectangle
# ``[left, bottom, width, height]`` in figure coordinates. The marginal axes
# share one dimension with the main axes.

# definitions for the axes
left, width = 0.1, 0.65
bottom, height = 0.1, 0.65
spacing = 0.005


rect_scatter = [left, bottom, width, height]
rect_histx = [left, bottom + height + spacing, width, 0.2]
rect_histy = [left + width + spacing, bottom, 0.2, height]

# start with a square Figure
fig = plt.figure(figsize=(8, 8))

ax = fig.add_axes(rect_scatter)
ax_histx = fig.add_axes(rect_histx, sharex=ax)
ax_histy = fig.add_axes(rect_histy, sharey=ax)

# use the previously defined function
scatter_hist(x, y, ax, ax_histx, ax_histy)

plt.show()


#############################################################################
#
# Using a gridspec
# ----------------
# Defining the axes positions using a gridspec
# --------------------------------------------
#
# We may equally define a gridspec with unequal width- and height-ratios to
# achieve desired layout. Also see the :doc:`/tutorials/intermediate/gridspec`
# tutorial.

# start with a square Figure
fig = plt.figure(figsize=(8, 8))
# We define a gridspec with unequal width- and height-ratios to achieve desired
# layout. Also see the :doc:`/tutorials/intermediate/gridspec` tutorial.

# Add a gridspec with two rows and two columns and a ratio of 2 to 7 between
# Start with a square Figure.
fig = plt.figure(figsize=(6, 6))
# Add a gridspec with two rows and two columns and a ratio of 1 to 4 between
# the size of the marginal axes and the main axes in both directions.
# Also adjust the subplot parameters for a square plot.
gs = fig.add_gridspec(2, 2, width_ratios=(7, 2), height_ratios=(2, 7),
gs = fig.add_gridspec(2, 2, width_ratios=(4, 1), height_ratios=(1, 4),
left=0.1, right=0.9, bottom=0.1, top=0.9,
wspace=0.05, hspace=0.05)

# Create the Axes.
ax = fig.add_subplot(gs[1, 0])
ax_histx = fig.add_subplot(gs[0, 0], sharex=ax)
ax_histy = fig.add_subplot(gs[1, 1], sharey=ax)
# Draw the scatter plot and marginals.
scatter_hist(x, y, ax, ax_histx, ax_histy)


# use the previously defined function
#############################################################################
#
# Defining the axes positions using inset_axes
# --------------------------------------------
#
# `~.Axes.inset_axes` can be used to position marginals *outside* the main
# axes. The advantage of doing so is that the aspect ratio of the main axes
# can be fixed, and the marginals will always be drawn relative to the position
# of the axes.

# Create a Figure, which doesn't have to be square.
fig = plt.figure(constrained_layout=True)
# Create the main axes, leaving 25% of the figure space at the top and on the
# right to position marginals.
ax = fig.add_gridspec(top=0.75, right=0.75).subplots()
# The main axes' aspect can be fixed.
ax.set(aspect=1)
# Create marginal axes, which have 25% of the size of the main axes. Note that
# the inset axes are positioned *outside* (on the right and the top) of the
# main axes, by specifying axes coordinates greater than 1. Axes coordinates
# less than 0 would likewise specify positions on the left and the bottom of
# the main axes.
ax_histx = ax.inset_axes([0, 1.05, 1, 0.25], sharex=ax)
ax_histy = ax.inset_axes([1.05, 0, 0.25, 1], sharey=ax)
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You uses 2/7 before = 0.285. Is there a reason to use 0.25 here? Probably insignificant, but maybe change them to be the same?

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switched to 4:1 everywhere.

# Draw the scatter plot and marginals.
scatter_hist(x, y, ax, ax_histx, ax_histy)

plt.show()
Expand All @@ -118,8 +115,8 @@ def scatter_hist(x, y, ax, ax_histx, ax_histy):
# The use of the following functions, methods, classes and modules is shown
# in this example:
#
# - `matplotlib.figure.Figure.add_axes`
# - `matplotlib.figure.Figure.add_subplot`
# - `matplotlib.figure.Figure.add_gridspec`
# - `matplotlib.axes.Axes.inset_axes`
# - `matplotlib.axes.Axes.scatter`
# - `matplotlib.axes.Axes.hist`