matplotlib/tutorials/introductory/lifecycle.py at unpyplot · a52/matplotlib · GitHub

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"""

=======================

The Lifecycle of a Plot

=======================

This tutorial aims to show the beginning, middle, and end of a single

visualization using Matplotlib. We'll begin with some raw data and

end by saving a figure of a customized visualization. Along the way we'll try

to highlight some neat features and best-practices using Matplotlib.

.. currentmodule:: matplotlib

.. note::

This tutorial is based off of

`this excellent blog post <http://pbpython.com/effective-matplotlib.html>`_

by Chris Moffitt. It was transformed into this tutorial by Chris Holdgraf.

A note on the Object-Oriented API vs Pyplot

===========================================

Matplotlib has two interfaces. The first is an object-oriented (OO)

interface. In this case, we utilize an instance of :class:`axes.Axes`

in order to render visualizations on an instance of :class:`figure.Figure`.

The second is based on MATLAB and uses a state-based interface. This is

encapsulated in the :mod:`pyplot` module. See the :doc:`pyplot tutorials

</tutorials/introductory/pyplot>` for a more in-depth look at the pyplot

interface.

Most of the terms are straightforward but the main thing to remember

is that:

* The Figure is the final image that may contain 1 or more Axes.

* The Axes represent an individual plot (don't confuse this with the word

"axis", which refers to the x/y axis of a plot).

We call methods that do the plotting directly from the Axes, which gives

us much more flexibility and power in customizing our plot.

.. note::

In general, try to use the object-oriented interface over the pyplot

interface.

Our data

========

We'll use the data from the post from which this tutorial was derived.

It contains sales information for a number of companies.

"""

# sphinx_gallery_thumbnail_number = 10

import numpy as np

import matplotlib.pyplot as plt

from matplotlib.ticker import FuncFormatter

data = {'Barton LLC': 109438.50,

'Frami, Hills and Schmidt': 103569.59,

'Fritsch, Russel and Anderson': 112214.71,

'Jerde-Hilpert': 112591.43,

'Keeling LLC': 100934.30,

'Koepp Ltd': 103660.54,

'Kulas Inc': 137351.96,

'Trantow-Barrows': 123381.38,

'White-Trantow': 135841.99,

'Will LLC': 104437.60}

group_data = list(data.values())

group_names = list(data.keys())

group_mean = np.mean(group_data)

###############################################################################

# Getting started

# ===============

# This data is naturally visualized as a barplot, with one bar per

# group. To do this with the object-oriented approach, we'll first generate

# an instance of :class:`figure.Figure` and

# :class:`axes.Axes`. The Figure is like a canvas, and the Axes

# is a part of that canvas on which we will make a particular visualization.

# .. note::

# Figures can have multiple axes on them. For information on how to do this,

# see the :doc:`Tight Layout tutorial

# </tutorials/intermediate/tight_layout_guide>`.

fig, ax = plt.subplots()

###############################################################################

# Now that we have an Axes instance, we can plot on top of it.

fig, ax = plt.subplots()

ax.barh(group_names, group_data)

###############################################################################

# Controlling the style

# =====================

# There are many styles available in Matplotlib in order to let you tailor

# your visualization to your needs. To see a list of styles, we can use

# :mod:`pyplot.style`.

print(plt.style.available)

###############################################################################

# You can activate a style with the following:

plt.style.use('fivethirtyeight')

###############################################################################

# Now let's remake the above plot to see how it looks:

fig, ax = plt.subplots()

ax.barh(group_names, group_data)

###############################################################################

# The style controls many things, such as color, linewidths, backgrounds,

# etc.

# Customizing the plot

# ====================

# Now we've got a plot with the general look that we want, so let's fine-tune

# it so that it's ready for print. First let's rotate the labels on the x-axis

# so that they show up more clearly. We can gain access to these labels

# with the :meth:`axes.Axes.get_xticklabels` method:

fig, ax = plt.subplots()

ax.barh(group_names, group_data)

labels = ax.get_xticklabels()

###############################################################################

# If we'd like to set the property of many items at once, it's useful to use

# the :func:`pyplot.setp` function. This will take a list (or many lists) of

# Matplotlib objects, and attempt to set some style element of each one.

fig, ax = plt.subplots()

ax.barh(group_names, group_data)

labels = ax.get_xticklabels()

plt.setp(labels, rotation=45, horizontalalignment='right')

###############################################################################

# It looks like this cut off some of the labels on the bottom. We can

# tell Matplotlib to automatically make room for elements in the figures

# that we create. To do this we'll set the ``autolayout`` value of our

# rcParams. For more information on controlling the style, layout, and

# other features of plots with rcParams, see

# :doc:`/tutorials/introductory/customizing`.

plt.rcParams.update({'figure.autolayout': True})

fig, ax = plt.subplots()

ax.barh(group_names, group_data)

labels = ax.get_xticklabels()

plt.setp(labels, rotation=45, horizontalalignment='right')

###############################################################################

# Next, we'll add labels to the plot. To do this with the OO interface,

# we can use the :meth:`axes.Axes.set` method to set properties of this

# Axes object.

fig, ax = plt.subplots()

ax.barh(group_names, group_data)

labels = ax.get_xticklabels()

plt.setp(labels, rotation=45, horizontalalignment='right')

ax.set(xlim=[-10000, 140000], xlabel='Total Revenue', ylabel='Company',

title='Company Revenue')

###############################################################################

# We can also adjust the size of this plot using the :func:`pyplot.subplots`

# function. We can do this with the ``figsize`` kwarg.

# .. note::

# While indexing in NumPy follows the form (row, column), the figsize

# kwarg follows the form (width, height). This follows conventions in

# visualization, which unfortunately are different from those of linear

# algebra.

fig, ax = plt.subplots(figsize=(8, 4))

ax.barh(group_names, group_data)

labels = ax.get_xticklabels()

plt.setp(labels, rotation=45, horizontalalignment='right')

ax.set(xlim=[-10000, 140000], xlabel='Total Revenue', ylabel='Company',

title='Company Revenue')

###############################################################################

# For labels, we can specify custom formatting guidelines in the form of

# functions by using the :class:`ticker.FuncFormatter` class. Below we'll

# define a function that takes an integer as input, and returns a string

# as an output.

def currency(x, pos):

"""The two args are the value and tick position"""

if x >= 1e6:

s = '${:1.1f}M'.format(x*1e-6)

else:

s = '${:1.0f}K'.format(x*1e-3)

return s

formatter = FuncFormatter(currency)

###############################################################################

# We can then apply this formatter to the labels on our plot. To do this,

# we'll use the ``xaxis`` attribute of our axis. This lets you perform

# actions on a specific axis on our plot.

fig, ax = plt.subplots(figsize=(6, 8))

ax.barh(group_names, group_data)

labels = ax.get_xticklabels()

plt.setp(labels, rotation=45, horizontalalignment='right')

ax.set(xlim=[-10000, 140000], xlabel='Total Revenue', ylabel='Company',

title='Company Revenue')

ax.xaxis.set_major_formatter(formatter)

###############################################################################

# Combining multiple visualizations

# =================================

# It is possible to draw multiple plot elements on the same instance of

# :class:`axes.Axes`. To do this we simply need to call another one of

# the plot methods on that axes object.

fig, ax = plt.subplots(figsize=(8, 8))

ax.barh(group_names, group_data)

labels = ax.get_xticklabels()

plt.setp(labels, rotation=45, horizontalalignment='right')

# Add a vertical line, here we set the style in the function call

ax.axvline(group_mean, ls='--', color='r')

# Annotate new companies

for group in [3, 5, 8]:

ax.text(145000, group, "New Company", fontsize=10,

verticalalignment="center")

# Now we'll move our title up since it's getting a little cramped

ax.title.set(y=1.05)

ax.set(xlim=[-10000, 140000], xlabel='Total Revenue', ylabel='Company',

title='Company Revenue')

ax.xaxis.set_major_formatter(formatter)

ax.set_xticks([0, 25e3, 50e3, 75e3, 100e3, 125e3])

fig.subplots_adjust(right=.1)

plt.show()

###############################################################################

# Saving our plot

# ===============

# Now that we're happy with the outcome of our plot, we want to save it to

# disk. There are many file formats we can save to in Matplotlib. To see

# a list of available options, use:

print(fig.canvas.get_supported_filetypes())

###############################################################################

# We can then use the :meth:`figure.Figure.savefig` in order to save the figure

# to disk. Note that there are several useful flags we'll show below:

# * ``transparent=True`` makes the background of the saved figure transparent

# if the format supports it.

# * ``dpi=80`` controls the resolution (dots per square inch) of the output.

# * ``bbox_inches="tight"`` fits the bounds of the figure to our plot.

# Uncomment this line to save the figure.

# fig.savefig('sales.png', transparent=False, dpi=80, bbox_inches="tight")

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