.. only:: html
.. note::
:class: sphx-glr-download-link-note
Click :ref:`here ` to download the full example code
.. rst-class:: sphx-glr-example-title
.. _sphx_glr_tutorials_intermediate_constrainedlayout_guide.py:
================================
Constrained Layout Guide
================================
How to use constrained-layout to fit plots within your figure cleanly.
*constrained_layout* automatically adjusts subplots and decorations like
legends and colorbars so that they fit in the figure window while still
preserving, as best they can, the logical layout requested by the user.
*constrained_layout* is similar to
:doc:`tight_layout`,
but uses a constraint solver to determine the size of axes that allows
them to fit.
*constrained_layout* needs to be activated before any axes are added to
a figure. Two ways of doing so are
* using the respective argument to :func:`~.pyplot.subplots` or
:func:`~.pyplot.figure`, e.g.::
plt.subplots(constrained_layout=True)
* activate it via :ref:`rcParams`, like::
plt.rcParams['figure.constrained_layout.use'] = True
Those are described in detail throughout the following sections.
.. warning::
Currently Constrained Layout is **experimental**. The
behaviour and API are subject to change, or the whole functionality
may be removed without a deprecation period. If you *require* your
plots to be absolutely reproducible, get the Axes positions after
running Constrained Layout and use ``ax.set_position()`` in your code
with ``constrained_layout=False``.
Simple Example
==============
In Matplotlib, the location of axes (including subplots) are specified in
normalized figure coordinates. It can happen that your axis labels or
titles (or sometimes even ticklabels) go outside the figure area, and are thus
clipped.
.. code-block:: default
import matplotlib.pyplot as plt
import matplotlib.colors as mcolors
import matplotlib.gridspec as gridspec
import numpy as np
plt.rcParams['savefig.facecolor'] = "0.8"
plt.rcParams['figure.figsize'] = 4.5, 4.
plt.rcParams['figure.max_open_warning'] = 50
def example_plot(ax, fontsize=12, hide_labels=False):
ax.plot([1, 2])
ax.locator_params(nbins=3)
if hide_labels:
ax.set_xticklabels([])
ax.set_yticklabels([])
else:
ax.set_xlabel('x-label', fontsize=fontsize)
ax.set_ylabel('y-label', fontsize=fontsize)
ax.set_title('Title', fontsize=fontsize)
fig, ax = plt.subplots(constrained_layout=False)
example_plot(ax, fontsize=24)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_001.png
:alt: Title
:class: sphx-glr-single-img
To prevent this, the location of axes needs to be adjusted. For
subplots, this can be done by adjusting the subplot params
(:ref:`howto-subplots-adjust`). However, specifying your figure with the
``constrained_layout=True`` kwarg will do the adjusting automatically.
.. code-block:: default
fig, ax = plt.subplots(constrained_layout=True)
example_plot(ax, fontsize=24)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_002.png
:alt: Title
:class: sphx-glr-single-img
When you have multiple subplots, often you see labels of different
axes overlapping each other.
.. code-block:: default
fig, axs = plt.subplots(2, 2, constrained_layout=False)
for ax in axs.flat:
example_plot(ax)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_003.png
:alt: Title, Title, Title, Title
:class: sphx-glr-single-img
Specifying ``constrained_layout=True`` in the call to ``plt.subplots``
causes the layout to be properly constrained.
.. code-block:: default
fig, axs = plt.subplots(2, 2, constrained_layout=True)
for ax in axs.flat:
example_plot(ax)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_004.png
:alt: Title, Title, Title, Title
:class: sphx-glr-single-img
Colorbars
=========
If you create a colorbar with `.Figure.colorbar`,
you need to make room for it. ``constrained_layout`` does this
automatically. Note that if you specify ``use_gridspec=True`` it will be
ignored because this option is made for improving the layout via
``tight_layout``.
.. note::
For the `~.axes.Axes.pcolormesh` kwargs (``pc_kwargs``) we use a
dictionary. Below we will assign one colorbar to a number of axes each
containing a `~.cm.ScalarMappable`; specifying the norm and colormap
ensures the colorbar is accurate for all the axes.
.. code-block:: default
arr = np.arange(100).reshape((10, 10))
norm = mcolors.Normalize(vmin=0., vmax=100.)
# see note above: this makes all pcolormesh calls consistent:
pc_kwargs = {'rasterized': True, 'cmap': 'viridis', 'norm': norm}
fig, ax = plt.subplots(figsize=(4, 4), constrained_layout=True)
im = ax.pcolormesh(arr, **pc_kwargs)
fig.colorbar(im, ax=ax, shrink=0.6)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_005.png
:alt: constrainedlayout guide
:class: sphx-glr-single-img
.. rst-class:: sphx-glr-script-out
Out:
.. code-block:: none
If you specify a list of axes (or other iterable container) to the
``ax`` argument of ``colorbar``, constrained_layout will take space from
the specified axes.
.. code-block:: default
fig, axs = plt.subplots(2, 2, figsize=(4, 4), constrained_layout=True)
for ax in axs.flat:
im = ax.pcolormesh(arr, **pc_kwargs)
fig.colorbar(im, ax=axs, shrink=0.6)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_006.png
:alt: constrainedlayout guide
:class: sphx-glr-single-img
.. rst-class:: sphx-glr-script-out
Out:
.. code-block:: none
If you specify a list of axes from inside a grid of axes, the colorbar
will steal space appropriately, and leave a gap, but all subplots will
still be the same size.
.. code-block:: default
fig, axs = plt.subplots(3, 3, figsize=(4, 4), constrained_layout=True)
for ax in axs.flat:
im = ax.pcolormesh(arr, **pc_kwargs)
fig.colorbar(im, ax=axs[1:, ][:, 1], shrink=0.8)
fig.colorbar(im, ax=axs[:, -1], shrink=0.6)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_007.png
:alt: constrainedlayout guide
:class: sphx-glr-single-img
.. rst-class:: sphx-glr-script-out
Out:
.. code-block:: none
Suptitle
=========
``constrained_layout`` can also make room for `~.figure.Figure.suptitle`.
.. code-block:: default
fig, axs = plt.subplots(2, 2, figsize=(4, 4), constrained_layout=True)
for ax in axs.flat:
im = ax.pcolormesh(arr, **pc_kwargs)
fig.colorbar(im, ax=axs, shrink=0.6)
fig.suptitle('Big Suptitle')
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_008.png
:alt: Big Suptitle
:class: sphx-glr-single-img
.. rst-class:: sphx-glr-script-out
Out:
.. code-block:: none
Text(0.5, 0.98, 'Big Suptitle')
Legends
=======
Legends can be placed outside of their parent axis.
Constrained-layout is designed to handle this for :meth:`.Axes.legend`.
However, constrained-layout does *not* handle legends being created via
:meth:`.Figure.legend` (yet).
.. code-block:: default
fig, ax = plt.subplots(constrained_layout=True)
ax.plot(np.arange(10), label='This is a plot')
ax.legend(loc='center left', bbox_to_anchor=(0.8, 0.5))
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_009.png
:alt: constrainedlayout guide
:class: sphx-glr-single-img
.. rst-class:: sphx-glr-script-out
Out:
.. code-block:: none
However, this will steal space from a subplot layout:
.. code-block:: default
fig, axs = plt.subplots(1, 2, figsize=(4, 2), constrained_layout=True)
axs[0].plot(np.arange(10))
axs[1].plot(np.arange(10), label='This is a plot')
axs[1].legend(loc='center left', bbox_to_anchor=(0.8, 0.5))
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_010.png
:alt: constrainedlayout guide
:class: sphx-glr-single-img
.. rst-class:: sphx-glr-script-out
Out:
.. code-block:: none
In order for a legend or other artist to *not* steal space
from the subplot layout, we can ``leg.set_in_layout(False)``.
Of course this can mean the legend ends up
cropped, but can be useful if the plot is subsequently called
with ``fig.savefig('outname.png', bbox_inches='tight')``. Note,
however, that the legend's ``get_in_layout`` status will have to be
toggled again to make the saved file work, and we must manually
trigger a draw if we want constrained_layout to adjust the size
of the axes before printing.
.. code-block:: default
fig, axs = plt.subplots(1, 2, figsize=(4, 2), constrained_layout=True)
axs[0].plot(np.arange(10))
axs[1].plot(np.arange(10), label='This is a plot')
leg = axs[1].legend(loc='center left', bbox_to_anchor=(0.8, 0.5))
leg.set_in_layout(False)
# trigger a draw so that constrained_layout is executed once
# before we turn it off when printing....
fig.canvas.draw()
# we want the legend included in the bbox_inches='tight' calcs.
leg.set_in_layout(True)
# we don't want the layout to change at this point.
fig.set_constrained_layout(False)
fig.savefig('../../doc/_static/constrained_layout_1b.png',
bbox_inches='tight', dpi=100)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_011.png
:alt: constrainedlayout guide
:class: sphx-glr-single-img
The saved file looks like:
.. image:: /_static/constrained_layout_1b.png
:align: center
A better way to get around this awkwardness is to simply
use the legend method provided by `.Figure.legend`:
.. code-block:: default
fig, axs = plt.subplots(1, 2, figsize=(4, 2), constrained_layout=True)
axs[0].plot(np.arange(10))
lines = axs[1].plot(np.arange(10), label='This is a plot')
labels = [l.get_label() for l in lines]
leg = fig.legend(lines, labels, loc='center left',
bbox_to_anchor=(0.8, 0.5), bbox_transform=axs[1].transAxes)
fig.savefig('../../doc/_static/constrained_layout_2b.png',
bbox_inches='tight', dpi=100)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_012.png
:alt: constrainedlayout guide
:class: sphx-glr-single-img
The saved file looks like:
.. image:: /_static/constrained_layout_2b.png
:align: center
Padding and Spacing
===================
Padding between axes is controlled in the horizontal by *w_pad* and
*wspace*, and vertical by *h_pad* and *hspace*. These can be edited
via `~.figure.Figure.set_constrained_layout_pads`. *w/h_pad* are
the minimum space around the axes in units of inches:
.. code-block:: default
fig, axs = plt.subplots(2, 2, constrained_layout=True)
for ax in axs.flat:
example_plot(ax, hide_labels=True)
fig.set_constrained_layout_pads(w_pad=4 / 72, h_pad=4 / 72, hspace=0, wspace=0)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_013.png
:alt: constrainedlayout guide
:class: sphx-glr-single-img
Spacing between subplots is further set by *wspace* and *hspace*. These
are specified as a fraction of the size of the subplot group as a whole.
If these values are smaller than *w_pad* or *h_pad*, then the fixed pads are
used instead. Note in the below how the space at the edges doesn't change
from the above, but the space between subplots does.
.. code-block:: default
fig, axs = plt.subplots(2, 2, constrained_layout=True)
for ax in axs.flat:
example_plot(ax, hide_labels=True)
fig.set_constrained_layout_pads(w_pad=4 / 72, h_pad=4 / 72, hspace=0.2,
wspace=0.2)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_014.png
:alt: constrainedlayout guide
:class: sphx-glr-single-img
If there are more than two columns, the *wspace* is shared between them,
so here the wspace is divided in 2, with a *wspace* of 0.1 between each
column:
.. code-block:: default
fig, axs = plt.subplots(2, 3, constrained_layout=True)
for ax in axs.flat:
example_plot(ax, hide_labels=True)
fig.set_constrained_layout_pads(w_pad=4 / 72, h_pad=4 / 72, hspace=0.2,
wspace=0.2)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_015.png
:alt: constrainedlayout guide
:class: sphx-glr-single-img
GridSpecs also have optional *hspace* and *wspace* keyword arguments,
that will be used instead of the pads set by ``constrained_layout``:
.. code-block:: default
fig, axs = plt.subplots(2, 2, constrained_layout=True,
gridspec_kw={'wspace': 0.3, 'hspace': 0.2})
for ax in axs.flat:
example_plot(ax, hide_labels=True)
# this has no effect because the space set in the gridspec trumps the
# space set in constrained_layout.
fig.set_constrained_layout_pads(w_pad=4 / 72, h_pad=4 / 72, hspace=0.0,
wspace=0.0)
plt.show()
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_016.png
:alt: constrainedlayout guide
:class: sphx-glr-single-img
Spacing with colorbars
-----------------------
Colorbars are placed a distance *pad* from their parent, where *pad*
is a fraction of the width of the parent(s). The spacing to the
next subplot is then given by *w/hspace*.
.. code-block:: default
fig, axs = plt.subplots(2, 2, constrained_layout=True)
pads = [0, 0.05, 0.1, 0.2]
for pad, ax in zip(pads, axs.flat):
pc = ax.pcolormesh(arr, **pc_kwargs)
fig.colorbar(pc, ax=ax, shrink=0.6, pad=pad)
ax.set_xticklabels('')
ax.set_yticklabels('')
ax.set_title(f'pad: {pad}')
fig.set_constrained_layout_pads(w_pad=2 / 72, h_pad=2 / 72, hspace=0.2,
wspace=0.2)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_017.png
:alt: pad: 0, pad: 0.05, pad: 0.1, pad: 0.2
:class: sphx-glr-single-img
rcParams
========
There are five :ref:`rcParams` that can be set,
either in a script or in the :file:`matplotlibrc` file.
They all have the prefix ``figure.constrained_layout``:
- *use*: Whether to use constrained_layout. Default is False
- *w_pad*, *h_pad*: Padding around axes objects.
Float representing inches. Default is 3./72. inches (3 pts)
- *wspace*, *hspace*: Space between subplot groups.
Float representing a fraction of the subplot widths being separated.
Default is 0.02.
.. code-block:: default
plt.rcParams['figure.constrained_layout.use'] = True
fig, axs = plt.subplots(2, 2, figsize=(3, 3))
for ax in axs.flat:
example_plot(ax)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_018.png
:alt: Title, Title, Title, Title
:class: sphx-glr-single-img
Use with GridSpec
=================
constrained_layout is meant to be used
with :func:`~matplotlib.figure.Figure.subplots` or
:func:`~matplotlib.gridspec.GridSpec` and
:func:`~matplotlib.figure.Figure.add_subplot`.
Note that in what follows ``constrained_layout=True``
.. code-block:: default
fig = plt.figure()
gs1 = gridspec.GridSpec(2, 1, figure=fig)
ax1 = fig.add_subplot(gs1[0])
ax2 = fig.add_subplot(gs1[1])
example_plot(ax1)
example_plot(ax2)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_019.png
:alt: Title, Title
:class: sphx-glr-single-img
More complicated gridspec layouts are possible. Note here we use the
convenience functions `~.Figure.add_gridspec` and
`~.SubplotSpec.subgridspec`.
.. code-block:: default
fig = plt.figure()
gs0 = fig.add_gridspec(1, 2)
gs1 = gs0[0].subgridspec(2, 1)
ax1 = fig.add_subplot(gs1[0])
ax2 = fig.add_subplot(gs1[1])
example_plot(ax1)
example_plot(ax2)
gs2 = gs0[1].subgridspec(3, 1)
for ss in gs2:
ax = fig.add_subplot(ss)
example_plot(ax)
ax.set_title("")
ax.set_xlabel("")
ax.set_xlabel("x-label", fontsize=12)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_020.png
:alt: Title, Title
:class: sphx-glr-single-img
.. rst-class:: sphx-glr-script-out
Out:
.. code-block:: none
Text(0.5, 0, 'x-label')
Note that in the above the left and right columns don't have the same
vertical extent. If we want the top and bottom of the two grids to line up
then they need to be in the same gridspec. We need to make this figure
larger as well in order for the axes not to collapse to zero height:
.. code-block:: default
fig = plt.figure(figsize=(4, 6))
gs0 = fig.add_gridspec(6, 2)
ax1 = fig.add_subplot(gs0[:3, 0])
ax2 = fig.add_subplot(gs0[3:, 0])
example_plot(ax1)
example_plot(ax2)
ax = fig.add_subplot(gs0[0:2, 1])
example_plot(ax, hide_labels=True)
ax = fig.add_subplot(gs0[2:4, 1])
example_plot(ax, hide_labels=True)
ax = fig.add_subplot(gs0[4:, 1])
example_plot(ax, hide_labels=True)
fig.suptitle('Overlapping Gridspecs')
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_021.png
:alt: Overlapping Gridspecs, Title, Title
:class: sphx-glr-single-img
.. rst-class:: sphx-glr-script-out
Out:
.. code-block:: none
Text(0.5, 0.98, 'Overlapping Gridspecs')
This example uses two gridspecs to have the colorbar only pertain to
one set of pcolors. Note how the left column is wider than the
two right-hand columns because of this. Of course, if you wanted the
subplots to be the same size you only needed one gridspec.
.. code-block:: default
def docomplicated(suptitle=None):
fig = plt.figure()
gs0 = fig.add_gridspec(1, 2, figure=fig, width_ratios=[1., 2.])
gsl = gs0[0].subgridspec(2, 1)
gsr = gs0[1].subgridspec(2, 2)
for gs in gsl:
ax = fig.add_subplot(gs)
example_plot(ax)
axs = []
for gs in gsr:
ax = fig.add_subplot(gs)
pcm = ax.pcolormesh(arr, **pc_kwargs)
ax.set_xlabel('x-label')
ax.set_ylabel('y-label')
ax.set_title('title')
axs += [ax]
fig.colorbar(pcm, ax=axs)
if suptitle is not None:
fig.suptitle(suptitle)
docomplicated()
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_022.png
:alt: Title, Title, title, title, title, title
:class: sphx-glr-single-img
Manually setting axes positions
================================
There can be good reasons to manually set an axes position. A manual call
to `~.axes.Axes.set_position` will set the axes so constrained_layout has
no effect on it anymore. (Note that ``constrained_layout`` still leaves the
space for the axes that is moved).
.. code-block:: default
fig, axs = plt.subplots(1, 2)
example_plot(axs[0], fontsize=12)
axs[1].set_position([0.2, 0.2, 0.4, 0.4])
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_023.png
:alt: Title
:class: sphx-glr-single-img
Manually turning off ``constrained_layout``
===========================================
``constrained_layout`` usually adjusts the axes positions on each draw
of the figure. If you want to get the spacing provided by
``constrained_layout`` but not have it update, then do the initial
draw and then call ``fig.set_constrained_layout(False)``.
This is potentially useful for animations where the tick labels may
change length.
Note that ``constrained_layout`` is turned off for ``ZOOM`` and ``PAN``
GUI events for the backends that use the toolbar. This prevents the
axes from changing position during zooming and panning.
Limitations
===========
Incompatible functions
----------------------
``constrained_layout`` will work with `.pyplot.subplot`, but only if the
number of rows and columns is the same for each call.
The reason is that each call to `.pyplot.subplot` will create a new
`.GridSpec` instance if the geometry is not the same, and
``constrained_layout``. So the following works fine:
.. code-block:: default
fig = plt.figure()
ax1 = plt.subplot(2, 2, 1)
ax2 = plt.subplot(2, 2, 3)
# third axes that spans both rows in second column:
ax3 = plt.subplot(2, 2, (2, 4))
example_plot(ax1)
example_plot(ax2)
example_plot(ax3)
plt.suptitle('Homogenous nrows, ncols')
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_024.png
:alt: Homogenous nrows, ncols, Title, Title, Title
:class: sphx-glr-single-img
.. rst-class:: sphx-glr-script-out
Out:
.. code-block:: none
Text(0.5, 0.98, 'Homogenous nrows, ncols')
but the following leads to a poor layout:
.. code-block:: default
fig = plt.figure()
ax1 = plt.subplot(2, 2, 1)
ax2 = plt.subplot(2, 2, 3)
ax3 = plt.subplot(1, 2, 2)
example_plot(ax1)
example_plot(ax2)
example_plot(ax3)
plt.suptitle('Mixed nrows, ncols')
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_025.png
:alt: Mixed nrows, ncols, Title, Title, Title
:class: sphx-glr-single-img
.. rst-class:: sphx-glr-script-out
Out:
.. code-block:: none
Text(0.5, 0.98, 'Mixed nrows, ncols')
Similarly,
`~matplotlib.pyplot.subplot2grid` works with the same limitation
that nrows and ncols cannot change for the layout to look good.
.. code-block:: default
fig = plt.figure()
ax1 = plt.subplot2grid((3, 3), (0, 0))
ax2 = plt.subplot2grid((3, 3), (0, 1), colspan=2)
ax3 = plt.subplot2grid((3, 3), (1, 0), colspan=2, rowspan=2)
ax4 = plt.subplot2grid((3, 3), (1, 2), rowspan=2)
example_plot(ax1)
example_plot(ax2)
example_plot(ax3)
example_plot(ax4)
fig.suptitle('subplot2grid')
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_026.png
:alt: subplot2grid, Title, Title, Title, Title
:class: sphx-glr-single-img
.. rst-class:: sphx-glr-script-out
Out:
.. code-block:: none
Text(0.5, 0.98, 'subplot2grid')
Other Caveats
-------------
* ``constrained_layout`` only considers ticklabels, axis labels, titles, and
legends. Thus, other artists may be clipped and also may overlap.
* It assumes that the extra space needed for ticklabels, axis labels,
and titles is independent of original location of axes. This is
often true, but there are rare cases where it is not.
* There are small differences in how the backends handle rendering fonts,
so the results will not be pixel-identical.
* An artist using axes coordinates that extend beyond the axes
boundary will result in unusual layouts when added to an
axes. This can be avoided by adding the artist directly to the
:class:`~matplotlib.figure.Figure` using
:meth:`~matplotlib.figure.Figure.add_artist`. See
:class:`~matplotlib.patches.ConnectionPatch` for an example.
Debugging
=========
Constrained-layout can fail in somewhat unexpected ways. Because it uses
a constraint solver the solver can find solutions that are mathematically
correct, but that aren't at all what the user wants. The usual failure
mode is for all sizes to collapse to their smallest allowable value. If
this happens, it is for one of two reasons:
1. There was not enough room for the elements you were requesting to draw.
2. There is a bug - in which case open an issue at
https://github.com/matplotlib/matplotlib/issues.
If there is a bug, please report with a self-contained example that does
not require outside data or dependencies (other than numpy).
Notes on the algorithm
======================
The algorithm for the constraint is relatively straightforward, but
has some complexity due to the complex ways we can layout a figure.
Layout in Matplotlib is carried out with gridspecs
via the `~.GridSpec` class. A gridspec is a logical division of the figure
into rows and columns, with the relative width of the Axes in those
rows and columns set by *width_ratios* and *height_ratios*.
In constrained_layout, each gridspec gets a *layoutgrid* associated with
it. The *layoutgrid* has a series of ``left`` and ``right`` variables
for each column, and ``bottom`` and ``top`` variables for each row, and
further it has a margin for each of left, right, bottom and top. In each
row, the bottom/top margins are widened until all the decorators
in that row are accommodated. Similarly for columns and the left/right
margins.
Simple case: one Axes
---------------------
For a single Axes the layout is straight forward. There is one parent
layoutgrid for the figure consisting of one column and row, and
a child layoutgrid for the gridspec that contains the axes, again
consisting of one row and column. Space is made for the "decorations" on
each side of the axes. In the code, this is accomplished by the entries in
``do_constrained_layout()`` like::
gridspec._layoutgrid[0, 0].edit_margin_min('left',
-bbox.x0 + pos.x0 + w_pad)
where ``bbox`` is the tight bounding box of the axes, and ``pos`` its
position. Note how the four margins encompass the axes decorations.
.. code-block:: default
from matplotlib._layoutgrid import plot_children
fig, ax = plt.subplots(constrained_layout=True)
example_plot(ax, fontsize=24)
plot_children(fig, fig._layoutgrid)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_027.png
:alt: Title
:class: sphx-glr-single-img
Simple case: two Axes
---------------------
When there are multiple axes they have their layouts bound in
simple ways. In this example the left axes has much larger decorations
than the right, but they share a bottom margin, which is made large
enough to accommodate the larger xlabel. Same with the shared top
margin. The left and right margins are not shared, and hence are
allowed to be different.
.. code-block:: default
fig, ax = plt.subplots(1, 2, constrained_layout=True)
example_plot(ax[0], fontsize=32)
example_plot(ax[1], fontsize=8)
plot_children(fig, fig._layoutgrid, printit=False)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_028.png
:alt: Title, Title
:class: sphx-glr-single-img
Two Axes and colorbar
---------------------
A colorbar is simply another item that expands the margin of the parent
layoutgrid cell:
.. code-block:: default
fig, ax = plt.subplots(1, 2, constrained_layout=True)
im = ax[0].pcolormesh(arr, **pc_kwargs)
fig.colorbar(im, ax=ax[0], shrink=0.6)
im = ax[1].pcolormesh(arr, **pc_kwargs)
plot_children(fig, fig._layoutgrid)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_029.png
:alt: constrainedlayout guide
:class: sphx-glr-single-img
Colorbar associated with a Gridspec
-----------------------------------
If a colorbar belongs to more than one cell of the grid, then
it makes a larger margin for each:
.. code-block:: default
fig, axs = plt.subplots(2, 2, constrained_layout=True)
for ax in axs.flat:
im = ax.pcolormesh(arr, **pc_kwargs)
fig.colorbar(im, ax=axs, shrink=0.6)
plot_children(fig, fig._layoutgrid, printit=False)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_030.png
:alt: constrainedlayout guide
:class: sphx-glr-single-img
Uneven sized Axes
-----------------
There are two ways to make axes have an uneven size in a
Gridspec layout, either by specifying them to cross Gridspecs rows
or columns, or by specifying width and height ratios.
The first method is used here. Note that the middle ``top`` and
``bottom`` margins are not affected by the left-hand column. This
is a conscious decision of the algorithm, and leads to the case where
the two right-hand axes have the same height, but it is not 1/2 the height
of the left-hand axes. This is consietent with how ``gridspec`` works
without constrained layout.
.. code-block:: default
fig = plt.figure(constrained_layout=True)
gs = gridspec.GridSpec(2, 2, figure=fig)
ax = fig.add_subplot(gs[:, 0])
im = ax.pcolormesh(arr, **pc_kwargs)
ax = fig.add_subplot(gs[0, 1])
im = ax.pcolormesh(arr, **pc_kwargs)
ax = fig.add_subplot(gs[1, 1])
im = ax.pcolormesh(arr, **pc_kwargs)
plot_children(fig, fig._layoutgrid, printit=False)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_031.png
:alt: constrainedlayout guide
:class: sphx-glr-single-img
One case that requires finessing is if margins do not have any artists
constraining their width. In the case below, the right margin for column 0
and the left margin for column 3 have no margin artists to set their width,
so we take the maximum width of the margin widths that do have artists.
This makes all the axes have the same size:
.. code-block:: default
fig = plt.figure(constrained_layout=True)
gs = fig.add_gridspec(2, 4)
ax00 = fig.add_subplot(gs[0, 0:2])
ax01 = fig.add_subplot(gs[0, 2:])
ax10 = fig.add_subplot(gs[1, 1:3])
example_plot(ax10, fontsize=14)
plot_children(fig, fig._layoutgrid)
.. image:: /tutorials/intermediate/images/sphx_glr_constrainedlayout_guide_032.png
:alt: Title
:class: sphx-glr-single-img
.. rst-class:: sphx-glr-timing
**Total running time of the script:** ( 0 minutes 12.131 seconds)
.. _sphx_glr_download_tutorials_intermediate_constrainedlayout_guide.py:
.. only :: html
.. container:: sphx-glr-footer
:class: sphx-glr-footer-example
.. container:: sphx-glr-download sphx-glr-download-python
:download:`Download Python source code: constrainedlayout_guide.py `
.. container:: sphx-glr-download sphx-glr-download-jupyter
:download:`Download Jupyter notebook: constrainedlayout_guide.ipynb `
.. only:: html
.. rst-class:: sphx-glr-signature
Keywords: matplotlib code example, codex, python plot, pyplot
`Gallery generated by Sphinx-Gallery
`_