Customizing Figure Layouts Using GridSpec and Other Functions

How to create grid-shaped combinations of axes.

subplots()

Perhaps the primary function used to create figures and axes. It's also similar to matplotlib.pyplot.subplot(), but creates and places all axes on the figure at once. See also matplotlib.figure.Figure.subplots.

GridSpec

Specifies the geometry of the grid that a subplot will be placed. The number of rows and number of columns of the grid need to be set. Optionally, the subplot layout parameters (e.g., left, right, etc.) can be tuned.

SubplotSpec

Specifies the location of the subplot in the given GridSpec.

subplot2grid()

A helper function that is similar to subplot(), but uses 0-based indexing and let subplot to occupy multiple cells. This function is not covered in this tutorial.

import matplotlib
import matplotlib.pyplot as plt
import matplotlib.gridspec as gridspec

Basic Quickstart Guide

These first two examples show how to create a basic 2-by-2 grid using both subplots() and gridspec.

Using subplots() is quite simple. It returns a Figure instance and an array of Axes objects.

fig1, f1_axes = plt.subplots(ncols=2, nrows=2, constrained_layout=True)

For a simple use case such as this, gridspec is perhaps overly verbose. You have to create the figure and GridSpec instance separately, then pass elements of gridspec instance to the add_subplot() method to create the axes objects. The elements of the gridspec are accessed in generally the same manner as numpy arrays.

fig2 = plt.figure(constrained_layout=True)
spec2 = gridspec.GridSpec(ncols=2, nrows=2, figure=fig2)
f2_ax1 = fig2.add_subplot(spec2[0, 0])
f2_ax2 = fig2.add_subplot(spec2[0, 1])
f2_ax3 = fig2.add_subplot(spec2[1, 0])
f2_ax4 = fig2.add_subplot(spec2[1, 1])

The power of gridspec comes in being able to create subplots that span rows and columns. Note the NumPy slice syntax for selecting the part of the gridspec each subplot will occupy.

Note that we have also used the convenience method Figure.add_gridspec instead of gridspec.GridSpec, potentially saving the user an import, and keeping the namespace cleaner.

fig3 = plt.figure(constrained_layout=True)
gs = fig3.add_gridspec(3, 3)
f3_ax1 = fig3.add_subplot(gs[0, :])
f3_ax1.set_title('gs[0, :]')
f3_ax2 = fig3.add_subplot(gs[1, :-1])
f3_ax2.set_title('gs[1, :-1]')
f3_ax3 = fig3.add_subplot(gs[1:, -1])
f3_ax3.set_title('gs[1:, -1]')
f3_ax4 = fig3.add_subplot(gs[-1, 0])
f3_ax4.set_title('gs[-1, 0]')
f3_ax5 = fig3.add_subplot(gs[-1, -2])
f3_ax5.set_title('gs[-1, -2]')

Out:

Text(0.5, 1.0, 'gs[-1, -2]')

gridspec is also indispensable for creating subplots of different widths via a couple of methods.

The method shown here is similar to the one above and initializes a uniform grid specification, and then uses numpy indexing and slices to allocate multiple "cells" for a given subplot.

fig4 = plt.figure(constrained_layout=True)
spec4 = fig4.add_gridspec(ncols=2, nrows=2)
anno_opts = dict(xy=(0.5, 0.5), xycoords='axes fraction',
                 va='center', ha='center')

f4_ax1 = fig4.add_subplot(spec4[0, 0])
f4_ax1.annotate('GridSpec[0, 0]', **anno_opts)
fig4.add_subplot(spec4[0, 1]).annotate('GridSpec[0, 1:]', **anno_opts)
fig4.add_subplot(spec4[1, 0]).annotate('GridSpec[1:, 0]', **anno_opts)
fig4.add_subplot(spec4[1, 1]).annotate('GridSpec[1:, 1:]', **anno_opts)

Out:

Text(0.5, 0.5, 'GridSpec[1:, 1:]')

Another option is to use the width_ratios and height_ratios parameters. These keyword arguments are lists of numbers. Note that absolute values are meaningless, only their relative ratios matter. That means that width_ratios=[2, 4, 8] is equivalent to width_ratios=[1, 2, 4] within equally wide figures. For the sake of demonstration, we'll blindly create the axes within for loops since we won't need them later.

fig5 = plt.figure(constrained_layout=True)
widths = [2, 3, 1.5]
heights = [1, 3, 2]
spec5 = fig5.add_gridspec(ncols=3, nrows=3, width_ratios=widths,
                          height_ratios=heights)
for row in range(3):
    for col in range(3):
        ax = fig5.add_subplot(spec5[row, col])
        label = 'Width: {}\nHeight: {}'.format(widths[col], heights[row])
        ax.annotate(label, (0.1, 0.5), xycoords='axes fraction', va='center')

Learning to use width_ratios and height_ratios is particularly useful since the top-level function subplots() accepts them within the gridspec_kw parameter. For that matter, any parameter accepted by GridSpec can be passed to subplots() via the gridspec_kw parameter. This example recreates the previous figure without directly using a gridspec instance.

gs_kw = dict(width_ratios=widths, height_ratios=heights)
fig6, f6_axes = plt.subplots(ncols=3, nrows=3, constrained_layout=True,
                             gridspec_kw=gs_kw)
for r, row in enumerate(f6_axes):
    for c, ax in enumerate(row):
        label = 'Width: {}\nHeight: {}'.format(widths[c], heights[r])
        ax.annotate(label, (0.1, 0.5), xycoords='axes fraction', va='center')

The subplots and get_gridspec methods can be combined since it is sometimes more convenient to make most of the subplots using subplots and then remove some and combine them. Here we create a layout with the bottom two axes in the last column combined.

fig7, f7_axs = plt.subplots(ncols=3, nrows=3)
gs = f7_axs[1, 2].get_gridspec()
# remove the underlying axes
for ax in f7_axs[1:, -1]:
    ax.remove()
axbig = fig7.add_subplot(gs[1:, -1])
axbig.annotate('Big Axes \nGridSpec[1:, -1]', (0.1, 0.5),
               xycoords='axes fraction', va='center')

fig7.tight_layout()

Fine Adjustments to a Gridspec Layout

When a GridSpec is explicitly used, you can adjust the layout parameters of subplots that are created from the GridSpec. Note this option is not compatible with constrained_layout or Figure.tight_layout which both adjust subplot sizes to fill the figure.

fig8 = plt.figure(constrained_layout=False)
gs1 = fig8.add_gridspec(nrows=3, ncols=3, left=0.05, right=0.48, wspace=0.05)
f8_ax1 = fig8.add_subplot(gs1[:-1, :])
f8_ax2 = fig8.add_subplot(gs1[-1, :-1])
f8_ax3 = fig8.add_subplot(gs1[-1, -1])

This is similar to subplots_adjust(), but it only affects the subplots that are created from the given GridSpec.

For example, compare the left and right sides of this figure:

fig9 = plt.figure(constrained_layout=False)
gs1 = fig9.add_gridspec(nrows=3, ncols=3, left=0.05, right=0.48,
                        wspace=0.05)
f9_ax1 = fig9.add_subplot(gs1[:-1, :])
f9_ax2 = fig9.add_subplot(gs1[-1, :-1])
f9_ax3 = fig9.add_subplot(gs1[-1, -1])

gs2 = fig9.add_gridspec(nrows=3, ncols=3, left=0.55, right=0.98,
                        hspace=0.05)
f9_ax4 = fig9.add_subplot(gs2[:, :-1])
f9_ax5 = fig9.add_subplot(gs2[:-1, -1])
f9_ax6 = fig9.add_subplot(gs2[-1, -1])

GridSpec using SubplotSpec

You can create GridSpec from the SubplotSpec, in which case its layout parameters are set to that of the location of the given SubplotSpec.

Note this is also available from the more verbose gridspec.GridSpecFromSubplotSpec.

fig10 = plt.figure(constrained_layout=True)
gs0 = fig10.add_gridspec(1, 2)

gs00 = gs0[0].subgridspec(2, 3)
gs01 = gs0[1].subgridspec(3, 2)

for a in range(2):
    for b in range(3):
        fig10.add_subplot(gs00[a, b])
        fig10.add_subplot(gs01[b, a])

A Complex Nested GridSpec using SubplotSpec

Here's a more sophisticated example of nested GridSpec where we put a box around each cell of the outer 4x4 grid, by hiding appropriate spines in each of the inner 3x3 grids.

import numpy as np


def squiggle_xy(a, b, c, d, i=np.arange(0.0, 2*np.pi, 0.05)):
    return np.sin(i*a)*np.cos(i*b), np.sin(i*c)*np.cos(i*d)


fig11 = plt.figure(figsize=(8, 8), constrained_layout=False)
outer_grid = fig11.add_gridspec(4, 4, wspace=0, hspace=0)

for a in range(4):
    for b in range(4):
        # gridspec inside gridspec
        inner_grid = outer_grid[a, b].subgridspec(3, 3, wspace=0, hspace=0)
        axs = inner_grid.subplots()  # Create all subplots for the inner grid.
        for (c, d), ax in np.ndenumerate(axs):
            ax.plot(*squiggle_xy(a + 1, b + 1, c + 1, d + 1))
            ax.set(xticks=[], yticks=[])

# show only the outside spines
for ax in fig11.get_axes():
    ax.spines['top'].set_visible(ax.is_first_row())
    ax.spines['bottom'].set_visible(ax.is_last_row())
    ax.spines['left'].set_visible(ax.is_first_col())
    ax.spines['right'].set_visible(ax.is_last_col())

plt.show()

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References

The usage of the following functions and methods is shown in this example:

matplotlib.pyplot.subplots
matplotlib.figure.Figure.add_gridspec
matplotlib.figure.Figure.add_subplot
matplotlib.gridspec.GridSpec
matplotlib.gridspec.SubplotSpec.subgridspec
matplotlib.gridspec.GridSpecFromSubplotSpec