"""

***********

Usage Guide

***********

This tutorial covers some basic usage patterns and best-practices to

help you get started with Matplotlib.

"""

# sphinx_gallery_thumbnail_number = 3

import matplotlib.pyplot as plt

import numpy as np

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

#

# A simple example

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

#

# Matplotlib graphs your data on `~.figure.Figure`\s (i.e., windows, Jupyter

# widgets, etc.), each of which can contain one or more `~.axes.Axes` (i.e., an

# area where points can be specified in terms of x-y coordinates (or theta-r

# in a polar plot, or x-y-z in a 3D plot, etc.). The most simple way of

# creating a figure with an axes is using `.pyplot.subplots`. We can then use

# `.Axes.plot` to draw some data on the axes:

fig, ax = plt.subplots() # Create a figure containing a single axes.

ax.plot([1, 2, 3, 4], [1, 4, 2, 3]) # Plot some data on the axes.

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

# Many other plotting libraries or languages do not require you to explicitly

# create an axes. For example, in MATLAB, one can just do

#

# .. code-block:: matlab

#

# plot([1, 2, 3, 4], [1, 4, 2, 3]) % MATLAB plot.

#

# and get the desired graph.

#

# In fact, you can do the same in Matplotlib: for each `~.axes.Axes` graphing

# method, there is a corresponding function in the :mod:`matplotlib.pyplot`

# module that performs that plot on the "current" axes, creating that axes (and

# its parent figure) if they don't exist yet. So the previous example can be

# written more shortly as

plt.plot([1, 2, 3, 4], [1, 4, 2, 3]) # Matplotlib plot.

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

# .. _figure_parts:

#

# Parts of a Figure

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

#

# Now, let's have a deeper look at the components of a Matplotlib figure.

#

# .. image:: ../../_static/anatomy.png

#

# :class:`~matplotlib.figure.Figure`

# ----------------------------------

#

# The **whole** figure. The figure keeps

# track of all the child :class:`~matplotlib.axes.Axes`, a smattering of

# 'special' artists (titles, figure legends, etc), and the **canvas**.

# (Don't worry too much about the canvas, it is crucial as it is the

# object that actually does the drawing to get you your plot, but as the

# user it is more-or-less invisible to you). A figure can contain any

# number of :class:`~matplotlib.axes.Axes`, but will typically have

# at least one.

#

# The easiest way to create a new figure is with pyplot::

#

# fig = plt.figure() # an empty figure with no Axes

# fig, ax = plt.subplots() # a figure with a single Axes

# fig, axs = plt.subplots(2, 2) # a figure with a 2x2 grid of Axes

#

# It's convenient to create the axes together with the figure, but you can

# also add axes later on, allowing for more complex axes layouts.

#

# :class:`~matplotlib.axes.Axes`

# ------------------------------

#

# This is what you think of as 'a plot', it is the region of the image

# with the data space. A given figure

# can contain many Axes, but a given :class:`~matplotlib.axes.Axes`

# object can only be in one :class:`~matplotlib.figure.Figure`. The

# Axes contains two (or three in the case of 3D)

# :class:`~matplotlib.axis.Axis` objects (be aware of the difference

# between **Axes** and **Axis**) which take care of the data limits (the

# data limits can also be controlled via the :meth:`.axes.Axes.set_xlim` and

# :meth:`.axes.Axes.set_ylim` methods). Each :class:`~.axes.Axes` has a title

# (set via :meth:`~matplotlib.axes.Axes.set_title`), an x-label (set via

# :meth:`~matplotlib.axes.Axes.set_xlabel`), and a y-label set via

# :meth:`~matplotlib.axes.Axes.set_ylabel`).

#

# The :class:`~.axes.Axes` class and its member functions are the primary entry

# point to working with the OO interface.

#

# :class:`~matplotlib.axis.Axis`

# ------------------------------

#

# These are the number-line-like objects. They take

# care of setting the graph limits and generating the ticks (the marks

# on the axis) and ticklabels (strings labeling the ticks). The location of

# the ticks is determined by a `~matplotlib.ticker.Locator` object and the

# ticklabel strings are formatted by a `~matplotlib.ticker.Formatter`. The

# combination of the correct `.Locator` and `.Formatter` gives very fine

# control over the tick locations and labels.

#

# :class:`~matplotlib.artist.Artist`

# ----------------------------------

#

# Basically everything you can see on the figure is an artist (even the

# `.Figure`, `Axes <.axes.Axes>`, and `~.axis.Axis` objects). This includes

# `.Text` objects, `.Line2D` objects, :mod:`.collections` objects, `.Patch`

# objects ... (you get the idea). When the figure is rendered, all of the

# artists are drawn to the **canvas**. Most Artists are tied to an Axes; such

# an Artist cannot be shared by multiple Axes, or moved from one to another.

#

# .. _input_types:

#

# Types of inputs to plotting functions

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

#

# All of plotting functions expect `numpy.array` or `numpy.ma.masked_array` as

# input. Classes that are 'array-like' such as `pandas` data objects

# and `numpy.matrix` may or may not work as intended. It is best to

# convert these to `numpy.array` objects prior to plotting.

#

# For example, to convert a `pandas.DataFrame` ::

#

# a = pandas.DataFrame(np.random.rand(4,5), columns = list('abcde'))

# a_asarray = a.values

#

# and to convert a `numpy.matrix` ::

#

# b = np.matrix([[1, 2], [3, 4]])

# b_asarray = np.asarray(b)

#

# .. _coding_styles:

#

# The object-oriented interface and the pyplot interface

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

#

# As noted above, there are essentially two ways to use Matplotlib:

#

# - Explicitly create figures and axes, and call methods on them (the

# "object-oriented (OO) style").

# - Rely on pyplot to automatically create and manage the figures and axes, and

# use pyplot functions for plotting.

#

# So one can do (OO-style)

x = np.linspace(0, 2, 100)

# Note that even in the OO-style, we use `.pyplot.figure` to create the figure.

fig, ax = plt.subplots() # Create a figure and an axes.

ax.plot(x, x, label='linear') # Plot some data on the axes.

ax.plot(x, x**2, label='quadratic') # Plot more data on the axes...

ax.plot(x, x**3, label='cubic') # ... and some more.

ax.set_xlabel('x label') # Add an x-label to the axes.

ax.set_ylabel('y label') # Add a y-label to the axes.

ax.set_title("Simple Plot") # Add a title to the axes.

ax.legend() # Add a legend.

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

# or (pyplot-style)

x = np.linspace(0, 2, 100)

plt.plot(x, x, label='linear') # Plot some data on the (implicit) axes.

plt.plot(x, x**2, label='quadratic') # etc.

plt.plot(x, x**3, label='cubic')

plt.xlabel('x label')

plt.ylabel('y label')

plt.title("Simple Plot")

plt.legend()

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

# Actually there is a third approach, for the case where you are embedding

# Matplotlib in a GUI application, which completely drops pyplot, even for

# figure creation. We won't discuss it here; see the corresponding section in

# the gallery for more info (:ref:`user_interfaces`).

#

# Matplotlib's documentation and examples use both the OO and the pyplot

# approaches (which are equally powerful), and you should feel free to use

# either (however, it is preferable pick one of them and stick to it, instead

# of mixing them). In general, we suggest to restrict pyplot to interactive

# plotting (e.g., in a Jupyter notebook), and to prefer the OO-style for

# non-interactive plotting (in functions and scripts that are intended to be

# reused as part of a larger project).

#

# .. note::

#

# In older examples, you may find examples that instead used the so-called

# ``pylab`` interface, via ``from pylab import *``. This star-import

# imports everything both from pyplot and from :mod:`numpy`, so that one

# could do ::

#

# x = linspace(0, 2, 100)

# plot(x, x, label='linear')

# ...

#

# for an even more MATLAB-like style. This approach is strongly discouraged

# nowadays and deprecated; it is only mentioned here because you may still

# encounter it in the wild.

#

# Typically one finds oneself making the same plots over and over

# again, but with different data sets, which leads to needing to write

# specialized functions to do the plotting. The recommended function

# signature is something like:

def my_plotter(ax, data1, data2, param_dict):

"""

A helper function to make a graph

Parameters

----------

ax : Axes

The axes to draw to

data1 : array

The x data

data2 : array

The y data

param_dict : dict

Dictionary of kwargs to pass to ax.plot

Returns

-------

out : list

list of artists added

"""

out = ax.plot(data1, data2, **param_dict)

return out

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

# which you would then use as:

data1, data2, data3, data4 = np.random.randn(4, 100)

fig, ax = plt.subplots(1, 1)

my_plotter(ax, data1, data2, {'marker': 'x'})

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

# or if you wanted to have 2 sub-plots:

fig, (ax1, ax2) = plt.subplots(1, 2)

my_plotter(ax1, data1, data2, {'marker': 'x'})

my_plotter(ax2, data3, data4, {'marker': 'o'})

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

# For these simple examples this style seems like overkill, however

# once the graphs get slightly more complex it pays off.

#

#

# .. _backends:

#

# Backends

# ========

#

# .. _what-is-a-backend:

#

# What is a backend?

# ------------------

#

# A lot of documentation on the website and in the mailing lists refers

# to the "backend" and many new users are confused by this term.

# matplotlib targets many different use cases and output formats. Some

# people use matplotlib interactively from the python shell and have

# plotting windows pop up when they type commands. Some people run

# `Jupyter <https://jupyter.org>`_ notebooks and draw inline plots for

# quick data analysis. Others embed matplotlib into graphical user

# interfaces like wxpython or pygtk to build rich applications. Some

# people use matplotlib in batch scripts to generate postscript images

# from numerical simulations, and still others run web application

# servers to dynamically serve up graphs.

#

# To support all of these use cases, matplotlib can target different

# outputs, and each of these capabilities is called a backend; the

# "frontend" is the user facing code, i.e., the plotting code, whereas the

# "backend" does all the hard work behind-the-scenes to make the figure.

# There are two types of backends: user interface backends (for use in

# pygtk, wxpython, tkinter, qt4, or macosx; also referred to as

# "interactive backends") and hardcopy backends to make image files

# (PNG, SVG, PDF, PS; also referred to as "non-interactive backends").

#

# Selecting a backend

# -------------------

#

# There are three ways to configure your backend:

#

# 1. The :rc:`backend` parameter in your ``matplotlibrc`` file

# 2. The :envvar:`MPLBACKEND` environment variable

# 3. The function :func:`matplotlib.use`

#

# A more detailed description is given below.

#

# If multiple of these are configurations are present, the last one from the

# list takes precedence; e.g. calling :func:`matplotlib.use()` will override

# the setting in your ``matplotlibrc``.

#

# If no backend is explicitly set, Matplotlib automatically detects a usable

# backend based on what is available on your system and on whether a GUI event

# loop is already running. On Linux, if the environment variable

# :envvar:`DISPLAY` is unset, the "event loop" is identified as "headless",

# which causes a fallback to a noninteractive backend (agg).

#

# Here is a detailed description of the configuration methods:

#

# #. Setting :rc:`backend` in your ``matplotlibrc`` file::

#

# backend : qt5agg # use pyqt5 with antigrain (agg) rendering

#

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

#

# #. Setting the :envvar:`MPLBACKEND` environment variable:

#

# You can set the environment variable either for your current shell or for

# a single script.

#

# On Unix::

#

# > export MPLBACKEND=qt5agg

# > python simple_plot.py

#

# > MPLBACKEND=qt5agg python simple_plot.py

#

# On Windows, only the former is possible::

#

# > set MPLBACKEND=qt5agg

# > python simple_plot.py

#

# Setting this environment variable will override the ``backend`` parameter

# in *any* ``matplotlibrc``, even if there is a ``matplotlibrc`` in your

# current working directory. Therefore, setting :envvar:`MPLBACKEND`

# globally, e.g. in your ``.bashrc`` or ``.profile``, is discouraged as it

# might lead to counter-intuitive behavior.

#

# #. If your script depends on a specific backend you can use the function

# :func:`matplotlib.use`::

#

# import matplotlib

# matplotlib.use('qt5agg')

#

# This should be done before any figure is created; otherwise Matplotlib may

# fail to switch the backend and raise an ImportError.

#

# Using `~matplotlib.use` will require changes in your code if users want to

# use a different backend. Therefore, you should avoid explicitly calling

# `~matplotlib.use` unless absolutely necessary.

#

#

# The builtin backends

# --------------------

#

# By default, Matplotlib should automatically select a default backend which

# allows both interactive work and plotting from scripts, with output to the

# screen and/or to a file, so at least initially you will not need to worry

# about the backend. The most common exception is if your Python distribution

# comes without :mod:`tkinter` and you have no other GUI toolkit installed;

# this happens on certain Linux distributions, where you need to install a

# Linux package named ``python-tk`` (or similar).

#

# If, however, you want to write graphical user interfaces, or a web

# application server (:ref:`howto-webapp`), or need a better

# understanding of what is going on, read on. To make things a little

# more customizable for graphical user interfaces, matplotlib separates

# the concept of the renderer (the thing that actually does the drawing)

# from the canvas (the place where the drawing goes). The canonical

# renderer for user interfaces is ``Agg`` which uses the `Anti-Grain

# Geometry`_ C++ library to make a raster (pixel) image of the figure; it

# is used by the ``Qt5Agg``, ``Qt4Agg``, ``GTK3Agg``, ``wxAgg``, ``TkAgg``, and

# ``macosx`` backends. An alternative renderer is based on the Cairo library,

# used by ``Qt5Cairo``, ``Qt4Cairo``, etc.

#

# For the rendering engines, one can also distinguish between `vector

# <https://en.wikipedia.org/wiki/Vector_graphics>`_ or `raster

# <https://en.wikipedia.org/wiki/Raster_graphics>`_ renderers. Vector

# graphics languages issue drawing commands like "draw a line from this

# point to this point" and hence are scale free, and raster backends

# generate a pixel representation of the line whose accuracy depends on a

# DPI setting.

#

# Here is a summary of the matplotlib renderers (there is an eponymous

# backend for each; these are *non-interactive backends*, capable of

# writing to a file):

#

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

# Renderer Filetypes Description

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

# AGG png raster_ graphics -- high quality images using the

# `Anti-Grain Geometry`_ engine

# PS ps, vector_ graphics -- Postscript_ output

# eps

# PDF pdf vector_ graphics -- `Portable Document Format`_

# SVG svg vector_ graphics -- `Scalable Vector Graphics`_

# Cairo png, ps, raster_ or vector_ graphics -- using the Cairo_ library

# pdf, svg

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

#

# To save plots using the non-interactive backends, use the

# ``matplotlib.pyplot.savefig('filename')`` method.

#

# And here are the user interfaces and renderer combinations supported;

# these are *interactive backends*, capable of displaying to the screen

# and of using appropriate renderers from the table above to write to

# a file:

#

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

# Backend Description

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

# Qt5Agg Agg rendering in a :term:`Qt5` canvas (requires PyQt5_). This

# backend can be activated in IPython with ``%matplotlib qt5``.

# ipympl Agg rendering embedded in a Jupyter widget. (requires ipympl).

# This backend can be enabled in a Jupyter notebook with

# ``%matplotlib ipympl``.

# GTK3Agg Agg rendering to a :term:`GTK` 3.x canvas (requires PyGObject_,

# and pycairo_ or cairocffi_). This backend can be activated in

# IPython with ``%matplotlib gtk3``.

# macosx Agg rendering into a Cocoa canvas in OSX. This backend can be

# activated in IPython with ``%matplotlib osx``.

# TkAgg Agg rendering to a :term:`Tk` canvas (requires TkInter_). This

# backend can be activated in IPython with ``%matplotlib tk``.

# nbAgg Embed an interactive figure in a Jupyter classic notebook. This

# backend can be enabled in Jupyter notebooks via

# ``%matplotlib notebook``.

# WebAgg On ``show()`` will start a tornado server with an interactive

# figure.

# GTK3Cairo Cairo rendering to a :term:`GTK` 3.x canvas (requires PyGObject_,

# and pycairo_ or cairocffi_).

# Qt4Agg Agg rendering to a :term:`Qt4` canvas (requires PyQt4_ or

# ``pyside``). This backend can be activated in IPython with

# ``%matplotlib qt4``.

# wxAgg Agg rendering to a :term:`wxWidgets` canvas (requires wxPython_ 4).

# This backend can be activated in IPython with ``%matplotlib wx``.

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

#

# .. note::

# The names of builtin backends case-insensitive; e.g., 'Qt5Agg' and

# 'qt5agg' are equivalent.

#

# .. _`Anti-Grain Geometry`: http://antigrain.com/

# .. _Postscript: https://en.wikipedia.org/wiki/PostScript

# .. _`Portable Document Format`: https://en.wikipedia.org/wiki/Portable_Document_Format

# .. _`Scalable Vector Graphics`: https://en.wikipedia.org/wiki/Scalable_Vector_Graphics

# .. _Cairo: https://www.cairographics.org

# .. _PyGObject: https://wiki.gnome.org/action/show/Projects/PyGObject

# .. _pycairo: https://www.cairographics.org/pycairo/

# .. _cairocffi: https://pythonhosted.org/cairocffi/

# .. _wxPython: https://www.wxpython.org/

# .. _TkInter: https://docs.python.org/3/library/tk.html

# .. _PyQt4: https://riverbankcomputing.com/software/pyqt/intro

# .. _PyQt5: https://riverbankcomputing.com/software/pyqt/intro

#

# ipympl

# ^^^^^^

#

# The Jupyter widget ecosystem is moving too fast to support directly in

# Matplotlib. To install ipympl

#

# .. code-block:: bash

#

# pip install ipympl

# jupyter nbextension enable --py --sys-prefix ipympl

#

# or

#

# .. code-block:: bash

#

# conda install ipympl -c conda-forge

#

# See `jupyter-matplotlib <https://github.com/matplotlib/jupyter-matplotlib>`__

# for more details.

#

# GTK and Cairo

# ^^^^^^^^^^^^^

#

# ``GTK3`` backends (*both* ``GTK3Agg`` and ``GTK3Cairo``) depend on Cairo

# (pycairo>=1.11.0 or cairocffi).

#

# .. _QT_API-usage:

#

# How do I select PyQt4 or PySide?

# ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

#

# The :envvar:`QT_API` environment variable can be set to either ``pyqt`` or

# ``pyside`` to use ``PyQt4`` or ``PySide``, respectively.

#

# Since the default value for the bindings to be used is ``PyQt4``, Matplotlib

# first tries to import it, if the import fails, it tries to import ``PySide``.

#

# Using non-builtin backends

# --------------------------

# More generally, any importable backend can be selected by using any of the

# methods above. If ``name.of.the.backend`` is the module containing the

# backend, use ``module://name.of.the.backend`` as the backend name, e.g.

# ``matplotlib.use('module://name.of.the.backend')``.

#

#

# .. _interactive-mode:

#

# What is interactive mode?

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

#

# Use of an interactive backend (see :ref:`what-is-a-backend`)

# permits--but does not by itself require or ensure--plotting

# to the screen. Whether and when plotting to the screen occurs,

# and whether a script or shell session continues after a plot

# is drawn on the screen, depends on the functions and methods

# that are called, and on a state variable that determines whether

# matplotlib is in "interactive mode". The default Boolean value is set

# by the :file:`matplotlibrc` file, and may be customized like any other

# configuration parameter (see :doc:`/tutorials/introductory/customizing`). It

# may also be set via :func:`matplotlib.interactive`, and its

# value may be queried via :func:`matplotlib.is_interactive`. Turning

# interactive mode on and off in the middle of a stream of plotting

# commands, whether in a script or in a shell, is rarely needed

# and potentially confusing, so in the following we will assume all

# plotting is done with interactive mode either on or off.

#

# .. note::

# Major changes related to interactivity, and in particular the

# role and behavior of :func:`~matplotlib.pyplot.show`, were made in the

# transition to matplotlib version 1.0, and bugs were fixed in

# 1.0.1. Here we describe the version 1.0.1 behavior for the

# primary interactive backends, with the partial exception of

# *macosx*.

#

# Interactive mode may also be turned on via :func:`matplotlib.pyplot.ion`,

# and turned off via :func:`matplotlib.pyplot.ioff`.

#

# .. note::

# Interactive mode works with suitable backends in ipython and in

# the ordinary python shell, but it does *not* work in the IDLE IDE.

# If the default backend does not support interactivity, an interactive

# backend can be explicitly activated using any of the methods discussed

# in `What is a backend?`_.

#

#

# Interactive example

# --------------------

#

# From an ordinary python prompt, or after invoking ipython with no options,

# try this::

#

# import matplotlib.pyplot as plt

# plt.ion()

# plt.plot([1.6, 2.7])

#

# This will pop up a plot window. Your terminal prompt will remain active, so

# that you can type additional commands such as::

#

# plt.title("interactive test")

# plt.xlabel("index")

#

# On most interactive backends, the figure window will also be updated if you

# change it via the object-oriented interface. E.g. get a reference to the

# `~matplotlib.axes.Axes` instance, and call a method of that instance::

#

# ax = plt.gca()

# ax.plot([3.1, 2.2])

#

# If you are using certain backends (like ``macosx``), or an older version

# of matplotlib, you may not see the new line added to the plot immediately.

# In this case, you need to explicitly call :func:`~matplotlib.pyplot.draw`

# in order to update the plot::

#

# plt.draw()

#

#

# Non-interactive example

# -----------------------

#

# Start a fresh session as in the previous example, but now

# turn interactive mode off::

#

# import matplotlib.pyplot as plt

# plt.ioff()

# plt.plot([1.6, 2.7])

#

# Nothing happened--or at least nothing has shown up on the

# screen (unless you are using *macosx* backend, which is

# anomalous). To make the plot appear, you need to do this::

#

# plt.show()

#

# Now you see the plot, but your terminal command line is

# unresponsive; the :func:`.pyplot.show()` command *blocks* the input

# of additional commands until you manually kill the plot

# window.

#

# What good is this--being forced to use a blocking function?

# Suppose you need a script that plots the contents of a file

# to the screen. You want to look at that plot, and then end

# the script. Without some blocking command such as ``show()``, the

# script would flash up the plot and then end immediately,

# leaving nothing on the screen.

#

# In addition, non-interactive mode delays all drawing until

# ``show()`` is called; this is more efficient than redrawing

# the plot each time a line in the script adds a new feature.

#

# Prior to version 1.0, ``show()`` generally could not be called

# more than once in a single script (although sometimes one

# could get away with it); for version 1.0.1 and above, this

# restriction is lifted, so one can write a script like this::

#

# import numpy as np

# import matplotlib.pyplot as plt

#

# plt.ioff()

# for i in range(3):

# plt.plot(np.random.rand(10))

# plt.show()

#

# which makes three plots, one at a time. I.e. the second plot will show up,

# once the first plot is closed.

#

# Summary

# -------

#

# In interactive mode, pyplot functions automatically draw

# to the screen.

#

# When plotting interactively, if using

# object method calls in addition to pyplot functions, then

# call :func:`~matplotlib.pyplot.draw` whenever you want to

# refresh the plot.

#

# Use non-interactive mode in scripts in which you want to

# generate one or more figures and display them before ending

# or generating a new set of figures. In that case, use

# :func:`~matplotlib.pyplot.show` to display the figure(s) and

# to block execution until you have manually destroyed them.

#

# .. _performance:

#

# Performance

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

#

# Whether exploring data in interactive mode or programmatically

# saving lots of plots, rendering performance can be a painful

# bottleneck in your pipeline. Matplotlib provides a couple

# ways to greatly reduce rendering time at the cost of a slight

# change (to a settable tolerance) in your plot's appearance.

# The methods available to reduce rendering time depend on the

# type of plot that is being created.

#

# Line segment simplification

# ---------------------------

#

# For plots that have line segments (e.g. typical line plots,

# outlines of polygons, etc.), rendering performance can be

# controlled by the ``path.simplify`` and

# ``path.simplify_threshold`` parameters in your

# ``matplotlibrc`` file (see

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

# more information about the ``matplotlibrc`` file).

# The ``path.simplify`` parameter is a boolean indicating whether

# or not line segments are simplified at all. The

# ``path.simplify_threshold`` parameter controls how much line

# segments are simplified; higher thresholds result in quicker

# rendering.

#

# The following script will first display the data without any

# simplification, and then display the same data with simplification.

# Try interacting with both of them::

#

# import numpy as np

# import matplotlib.pyplot as plt

# import matplotlib as mpl

#

# # Setup, and create the data to plot

# y = np.random.rand(100000)

# y[50000:] *= 2

# y[np.logspace(1, np.log10(50000), 400).astype(int)] = -1

# mpl.rcParams['path.simplify'] = True

#

# mpl.rcParams['path.simplify_threshold'] = 0.0

# plt.plot(y)

# plt.show()

#

# mpl.rcParams['path.simplify_threshold'] = 1.0

# plt.plot(y)

# plt.show()

#

# Matplotlib currently defaults to a conservative simplification

# threshold of ``1/9``. If you want to change your default settings

# to use a different value, you can change your ``matplotlibrc``

# file. Alternatively, you could create a new style for

# interactive plotting (with maximal simplification) and another

# style for publication quality plotting (with minimal

# simplification) and activate them as necessary. See

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

# instructions on how to perform these actions.

#

# The simplification works by iteratively merging line segments

# into a single vector until the next line segment's perpendicular

# distance to the vector (measured in display-coordinate space)

# is greater than the ``path.simplify_threshold`` parameter.

#

# .. note::

# Changes related to how line segments are simplified were made

# in version 2.1. Rendering time will still be improved by these

# parameters prior to 2.1, but rendering time for some kinds of

# data will be vastly improved in versions 2.1 and greater.

#

# Marker simplification

# ---------------------

#

# Markers can also be simplified, albeit less robustly than

# line segments. Marker simplification is only available

# to :class:`~matplotlib.lines.Line2D` objects (through the

# ``markevery`` property). Wherever

# :class:`~matplotlib.lines.Line2D` construction parameters

# are passed through, such as

# :func:`matplotlib.pyplot.plot` and

# :meth:`matplotlib.axes.Axes.plot`, the ``markevery``

# parameter can be used::

#

# plt.plot(x, y, markevery=10)

#

# The markevery argument allows for naive subsampling, or an

# attempt at evenly spaced (along the *x* axis) sampling. See the

# :doc:`/gallery/lines_bars_and_markers/markevery_demo`

# for more information.

#

# Splitting lines into smaller chunks

# -----------------------------------

#

# If you are using the Agg backend (see :ref:`what-is-a-backend`),

# then you can make use of the ``agg.path.chunksize`` rc parameter.

# This allows you to specify a chunk size, and any lines with

# greater than that many vertices will be split into multiple

# lines, each of which has no more than ``agg.path.chunksize``

# many vertices. (Unless ``agg.path.chunksize`` is zero, in

# which case there is no chunking.) For some kind of data,

# chunking the line up into reasonable sizes can greatly

# decrease rendering time.

#

# The following script will first display the data without any

# chunk size restriction, and then display the same data with

# a chunk size of 10,000. The difference can best be seen when

# the figures are large, try maximizing the GUI and then

# interacting with them::

#

# import numpy as np

# import matplotlib.pyplot as plt

# import matplotlib as mpl

# mpl.rcParams['path.simplify_threshold'] = 1.0

#

# # Setup, and create the data to plot

# y = np.random.rand(100000)

# y[50000:] *= 2

# y[np.logspace(1, np.log10(50000), 400).astype(int)] = -1

# mpl.rcParams['path.simplify'] = True

#

# mpl.rcParams['agg.path.chunksize'] = 0

# plt.plot(y)

# plt.show()

#

# mpl.rcParams['agg.path.chunksize'] = 10000

# plt.plot(y)

# plt.show()

#

# Legends

# -------

#

# The default legend behavior for axes attempts to find the location

# that covers the fewest data points (``loc='best'``). This can be a

# very expensive computation if there are lots of data points. In

# this case, you may want to provide a specific location.

#

# Using the *fast* style

# ----------------------

#

# The *fast* style can be used to automatically set

# simplification and chunking parameters to reasonable

# settings to speed up plotting large amounts of data.

# It can be used simply by running::

#

# import matplotlib.style as mplstyle

# mplstyle.use('fast')

#

# It is very light weight, so it plays nicely with other

# styles, just make sure the fast style is applied last

# so that other styles do not overwrite the settings::

#

# mplstyle.use(['dark_background', 'ggplot', 'fast'])