Files
notes_estom/Python/matplotlab/intermediate/tight_layout_guide.md
2020-09-26 22:03:11 +08:00

418 lines
13 KiB
Markdown

---
sidebarDepth: 3
sidebar: auto
---
# Tight Layout guide
How to use tight-layout to fit plots within your figure cleanly.
*tight_layout* automatically adjusts subplot params so that the
subplot(s) fits in to the figure area. This is an experimental
feature and may not work for some cases. It only checks the extents
of ticklabels, axis labels, and titles.
An alternative to *tight_layout* is [constrained_layout](constrainedlayout_guide.html).
## 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.
``` python
# sphinx_gallery_thumbnail_number = 7
import matplotlib.pyplot as plt
import numpy as np
plt.rcParams['savefig.facecolor'] = "0.8"
def example_plot(ax, fontsize=12):
ax.plot([1, 2])
ax.locator_params(nbins=3)
ax.set_xlabel('x-label', fontsize=fontsize)
ax.set_ylabel('y-label', fontsize=fontsize)
ax.set_title('Title', fontsize=fontsize)
plt.close('all')
fig, ax = plt.subplots()
example_plot(ax, fontsize=24)
```
![sphx_glr_tight_layout_guide_001](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_001.png)
To prevent this, the location of axes needs to be adjusted. For
subplots, this can be done by adjusting the subplot params
([Move the edge of an axes to make room for tick labels](https://matplotlib.orgfaq/howto_faq.html#howto-subplots-adjust)). Matplotlib v1.1 introduces a new
command [``tight_layout()``](https://matplotlib.orgapi/_as_gen/matplotlib.pyplot.tight_layout.html#matplotlib.pyplot.tight_layout) that does this
automatically for you.
``` python
fig, ax = plt.subplots()
example_plot(ax, fontsize=24)
plt.tight_layout()
```
![sphx_glr_tight_layout_guide_002](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_002.png)
Note that [``matplotlib.pyplot.tight_layout()``](https://matplotlib.orgapi/_as_gen/matplotlib.pyplot.tight_layout.html#matplotlib.pyplot.tight_layout) will only adjust the
subplot params when it is called. In order to perform this adjustment each
time the figure is redrawn, you can call ``fig.set_tight_layout(True)``, or,
equivalently, set the ``figure.autolayout`` rcParam to ``True``.
When you have multiple subplots, often you see labels of different
axes overlapping each other.
``` python
plt.close('all')
fig, ((ax1, ax2), (ax3, ax4)) = plt.subplots(nrows=2, ncols=2)
example_plot(ax1)
example_plot(ax2)
example_plot(ax3)
example_plot(ax4)
```
![sphx_glr_tight_layout_guide_003](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_003.png)
[``tight_layout()``](https://matplotlib.orgapi/_as_gen/matplotlib.pyplot.tight_layout.html#matplotlib.pyplot.tight_layout) will also adjust spacing between
subplots to minimize the overlaps.
``` python
fig, ((ax1, ax2), (ax3, ax4)) = plt.subplots(nrows=2, ncols=2)
example_plot(ax1)
example_plot(ax2)
example_plot(ax3)
example_plot(ax4)
plt.tight_layout()
```
![sphx_glr_tight_layout_guide_004](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_004.png)
[``tight_layout()``](https://matplotlib.orgapi/_as_gen/matplotlib.pyplot.tight_layout.html#matplotlib.pyplot.tight_layout) can take keyword arguments of
*pad*, *w_pad* and *h_pad*. These control the extra padding around the
figure border and between subplots. The pads are specified in fraction
of fontsize.
``` python
fig, ((ax1, ax2), (ax3, ax4)) = plt.subplots(nrows=2, ncols=2)
example_plot(ax1)
example_plot(ax2)
example_plot(ax3)
example_plot(ax4)
plt.tight_layout(pad=0.4, w_pad=0.5, h_pad=1.0)
```
![sphx_glr_tight_layout_guide_005](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_005.png)
[``tight_layout()``](https://matplotlib.orgapi/_as_gen/matplotlib.pyplot.tight_layout.html#matplotlib.pyplot.tight_layout) will work even if the sizes of
subplots are different as far as their grid specification is
compatible. In the example below, *ax1* and *ax2* are subplots of a 2x2
grid, while *ax3* is of a 1x2 grid.
``` python
plt.close('all')
fig = plt.figure()
ax1 = plt.subplot(221)
ax2 = plt.subplot(223)
ax3 = plt.subplot(122)
example_plot(ax1)
example_plot(ax2)
example_plot(ax3)
plt.tight_layout()
```
![sphx_glr_tight_layout_guide_006](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_006.png)
It works with subplots created with
[``subplot2grid()``](https://matplotlib.orgapi/_as_gen/matplotlib.pyplot.subplot2grid.html#matplotlib.pyplot.subplot2grid). In general, subplots created
from the gridspec ([Customizing Figure Layouts Using GridSpec and Other Functions](gridspec.html)) will work.
``` python
plt.close('all')
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)
plt.tight_layout()
```
![sphx_glr_tight_layout_guide_007](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_007.png)
Although not thoroughly tested, it seems to work for subplots with
aspect != "auto" (e.g., axes with images).
``` python
arr = np.arange(100).reshape((10, 10))
plt.close('all')
fig = plt.figure(figsize=(5, 4))
ax = plt.subplot(111)
im = ax.imshow(arr, interpolation="none")
plt.tight_layout()
```
![sphx_glr_tight_layout_guide_008](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_008.png)
## Caveats
- [``tight_layout()``](https://matplotlib.orgapi/_as_gen/matplotlib.pyplot.tight_layout.html#matplotlib.pyplot.tight_layout) only considers ticklabels, axis
labels, and titles. 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.
- pad=0 clips some of the texts by a few pixels. This may be a bug or
a limitation of the current algorithm and it is not clear why it
happens. Meanwhile, use of pad at least larger than 0.3 is
recommended.
## Use with GridSpec
GridSpec has its own [``tight_layout()``](https://matplotlib.orgapi/_as_gen/matplotlib.gridspec.GridSpec.html#matplotlib.gridspec.GridSpec.tight_layout) method
(the pyplot api [``tight_layout()``](https://matplotlib.orgapi/_as_gen/matplotlib.pyplot.tight_layout.html#matplotlib.pyplot.tight_layout) also works).
``` python
import matplotlib.gridspec as gridspec
plt.close('all')
fig = plt.figure()
gs1 = gridspec.GridSpec(2, 1)
ax1 = fig.add_subplot(gs1[0])
ax2 = fig.add_subplot(gs1[1])
example_plot(ax1)
example_plot(ax2)
gs1.tight_layout(fig)
```
![sphx_glr_tight_layout_guide_009](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_009.png)
You may provide an optional *rect* parameter, which specifies the bounding box
that the subplots will be fit inside. The coordinates must be in normalized
figure coordinates and the default is (0, 0, 1, 1).
``` python
fig = plt.figure()
gs1 = gridspec.GridSpec(2, 1)
ax1 = fig.add_subplot(gs1[0])
ax2 = fig.add_subplot(gs1[1])
example_plot(ax1)
example_plot(ax2)
gs1.tight_layout(fig, rect=[0, 0, 0.5, 1])
```
![sphx_glr_tight_layout_guide_010](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_010.png)
For example, this can be used for a figure with multiple gridspecs.
``` python
fig = plt.figure()
gs1 = gridspec.GridSpec(2, 1)
ax1 = fig.add_subplot(gs1[0])
ax2 = fig.add_subplot(gs1[1])
example_plot(ax1)
example_plot(ax2)
gs1.tight_layout(fig, rect=[0, 0, 0.5, 1])
gs2 = gridspec.GridSpec(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)
gs2.tight_layout(fig, rect=[0.5, 0, 1, 1], h_pad=0.5)
# We may try to match the top and bottom of two grids ::
top = min(gs1.top, gs2.top)
bottom = max(gs1.bottom, gs2.bottom)
gs1.update(top=top, bottom=bottom)
gs2.update(top=top, bottom=bottom)
plt.show()
```
![sphx_glr_tight_layout_guide_011](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_011.png)
While this should be mostly good enough, adjusting top and bottom
may require adjustment of hspace also. To update hspace & vspace, we
call [``tight_layout()``](https://matplotlib.orgapi/_as_gen/matplotlib.gridspec.GridSpec.html#matplotlib.gridspec.GridSpec.tight_layout) again with updated
rect argument. Note that the rect argument specifies the area including the
ticklabels, etc. Thus, we will increase the bottom (which is 0 for the normal
case) by the difference between the *bottom* from above and the bottom of each
gridspec. Same thing for the top.
``` python
fig = plt.gcf()
gs1 = gridspec.GridSpec(2, 1)
ax1 = fig.add_subplot(gs1[0])
ax2 = fig.add_subplot(gs1[1])
example_plot(ax1)
example_plot(ax2)
gs1.tight_layout(fig, rect=[0, 0, 0.5, 1])
gs2 = gridspec.GridSpec(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)
gs2.tight_layout(fig, rect=[0.5, 0, 1, 1], h_pad=0.5)
top = min(gs1.top, gs2.top)
bottom = max(gs1.bottom, gs2.bottom)
gs1.update(top=top, bottom=bottom)
gs2.update(top=top, bottom=bottom)
top = min(gs1.top, gs2.top)
bottom = max(gs1.bottom, gs2.bottom)
gs1.tight_layout(fig, rect=[None, 0 + (bottom-gs1.bottom),
0.5, 1 - (gs1.top-top)])
gs2.tight_layout(fig, rect=[0.5, 0 + (bottom-gs2.bottom),
None, 1 - (gs2.top-top)],
h_pad=0.5)
```
![sphx_glr_tight_layout_guide_012](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_012.png)
## Legends and Annotations
Pre Matplotlib 2.2, legends and annotations were excluded from the bounding
box calculations that decide the layout. Subsequently these artists were
added to the calculation, but sometimes it is undesirable to include them.
For instance in this case it might be good to have the axes shring a bit
to make room for the legend:
``` python
fig, ax = plt.subplots(figsize=(4, 3))
lines = ax.plot(range(10), label='A simple plot')
ax.legend(bbox_to_anchor=(0.7, 0.5), loc='center left',)
fig.tight_layout()
plt.show()
```
![sphx_glr_tight_layout_guide_013](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_013.png)
However, sometimes this is not desired (quite often when using
``fig.savefig('outname.png', bbox_inches='tight')``). In order to
remove the legend from the bounding box calculation, we simply set its
bounding ``leg.set_in_layout(False)`` and the legend will be ignored.
``` python
fig, ax = plt.subplots(figsize=(4, 3))
lines = ax.plot(range(10), label='B simple plot')
leg = ax.legend(bbox_to_anchor=(0.7, 0.5), loc='center left',)
leg.set_in_layout(False)
fig.tight_layout()
plt.show()
```
![sphx_glr_tight_layout_guide_014](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_014.png)
## Use with AxesGrid1
While limited, the axes_grid1 toolkit is also supported.
``` python
from mpl_toolkits.axes_grid1 import Grid
plt.close('all')
fig = plt.figure()
grid = Grid(fig, rect=111, nrows_ncols=(2, 2),
axes_pad=0.25, label_mode='L',
)
for ax in grid:
example_plot(ax)
ax.title.set_visible(False)
plt.tight_layout()
```
![sphx_glr_tight_layout_guide_015](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_015.png)
## Colorbar
If you create a colorbar with the [``colorbar()``](https://matplotlib.orgapi/_as_gen/matplotlib.pyplot.colorbar.html#matplotlib.pyplot.colorbar)
command, the created colorbar is an instance of Axes, *not* Subplot, so
tight_layout does not work. With Matplotlib v1.1, you may create a
colorbar as a subplot using the gridspec.
``` python
plt.close('all')
arr = np.arange(100).reshape((10, 10))
fig = plt.figure(figsize=(4, 4))
im = plt.imshow(arr, interpolation="none")
plt.colorbar(im, use_gridspec=True)
plt.tight_layout()
```
![sphx_glr_tight_layout_guide_016](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_016.png)
Another option is to use AxesGrid1 toolkit to
explicitly create an axes for colorbar.
``` python
from mpl_toolkits.axes_grid1 import make_axes_locatable
plt.close('all')
arr = np.arange(100).reshape((10, 10))
fig = plt.figure(figsize=(4, 4))
im = plt.imshow(arr, interpolation="none")
divider = make_axes_locatable(plt.gca())
cax = divider.append_axes("right", "5%", pad="3%")
plt.colorbar(im, cax=cax)
plt.tight_layout()
```
![sphx_glr_tight_layout_guide_017](https://matplotlib.org/_images/sphx_glr_tight_layout_guide_017.png)
**Total running time of the script:** ( 0 minutes 3.417 seconds)
## Download
- [Download Python source code: tight_layout_guide.py](https://matplotlib.org/_downloads/08204f760ca1d178acca434333c21c5c/tight_layout_guide.py)
- [Download Jupyter notebook: tight_layout_guide.ipynb](https://matplotlib.org/_downloads/967ce4dd04ce9628b993a5a4e402046a/tight_layout_guide.ipynb)