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"""
===============
Pyplot tutorial
===============
An introduction to the pyplot interface.
"""
###############################################################################
# Intro to pyplot
# ===============
#
# :mod:`matplotlib.pyplot` is a collection of command style functions
# that make matplotlib work like MATLAB.
# Each ``pyplot`` function makes
# some change to a figure: e.g., creates a figure, creates a plotting area
# in a figure, plots some lines in a plotting area, decorates the plot
# with labels, etc.
#
# In :mod:`matplotlib.pyplot` various states are preserved
# across function calls, so that it keeps track of things like
# the current figure and plotting area, and the plotting
# functions are directed to the current axes (please note that "axes" here
# and in most places in the documentation refers to the *axes*
# `part of a figure <http://matplotlib.org/faq/usage_faq.html#parts-of-a-figure>`__
# and not the strict mathematical term for more than one axis).
#
# .. note::
#
# the pyplot API is generally less-flexible than the object-oriented API.
# Most of the function calls you see here can also be called as methods
# from an ``Axes`` object. We recommend browsing the tutorials and
# examples to see how this works.
#
# Generating visualizations with pyplot is very quick:
import matplotlib.pyplot as plt
plt.plot([1, 2, 3, 4])
plt.ylabel('some numbers')
plt.show()
###############################################################################
# You may be wondering why the x-axis ranges from 0-3 and the y-axis
# from 1-4. If you provide a single list or array to the
# :func:`~matplotlib.pyplot.plot` command, matplotlib assumes it is a
# sequence of y values, and automatically generates the x values for
# you. Since python ranges start with 0, the default x vector has the
# same length as y but starts with 0. Hence the x data are
# ``[0,1,2,3]``.
#
# :func:`~matplotlib.pyplot.plot` is a versatile command, and will take
# an arbitrary number of arguments. For example, to plot x versus y,
# you can issue the command::
plt.plot([1, 2, 3, 4], [1, 4, 9, 16])
###############################################################################
# Formatting the style of your plot
# ---------------------------------
#
# For every x, y pair of arguments, there is an optional third argument
# which is the format string that indicates the color and line type of
# the plot. The letters and symbols of the format string are from
# MATLAB, and you concatenate a color string with a line style string.
# The default format string is 'b-', which is a solid blue line. For
# example, to plot the above with red circles, you would issue
plt.plot([1, 2, 3, 4], [1, 4, 9, 16], 'ro')
plt.axis([0, 6, 0, 20])
plt.show()
###############################################################################
# See the :func:`~matplotlib.pyplot.plot` documentation for a complete
# list of line styles and format strings. The
# :func:`~matplotlib.pyplot.axis` command in the example above takes a
# list of ``[xmin, xmax, ymin, ymax]`` and specifies the viewport of the
# axes.
#
# If matplotlib were limited to working with lists, it would be fairly
# useless for numeric processing. Generally, you will use `numpy
# <http://www.numpy.org>`_ arrays. In fact, all sequences are
# converted to numpy arrays internally. The example below illustrates a
# plotting several lines with different format styles in one command
# using arrays.
import numpy as np
# evenly sampled time at 200ms intervals
t = np.arange(0., 5., 0.2)
# red dashes, blue squares and green triangles
plt.plot(t, t, 'r--', t, t**2, 'bs', t, t**3, 'g^')
plt.show()
###############################################################################
# .. _plotting-with-keywords:
#
# Plotting with keyword strings
# =============================
#
# There are some instances where you have data in a format that lets you
# access particular variables with strings. For example, with
# :class:`numpy.recarray` or :class:`pandas.DataFrame`.
#
# Matplotlib allows you provide such an object with
# the ``data`` keyword argument. If provided, then you may generate plots with
# the strings corresponding to these variables.
data = {'a': np.arange(50),
'c': np.random.randint(0, 50, 50),
'd': np.random.randn(50)}
data['b'] = data['a'] + 10 * np.random.randn(50)
data['d'] = np.abs(data['d']) * 100
plt.scatter('a', 'b', c='c', s='d', data=data)
plt.xlabel('entry a')
plt.ylabel('entry b')
plt.show()
###############################################################################
# .. _plotting-with-categorical-vars:
#
# Plotting with categorical variables
# ===================================
#
# It is also possible to create a plot using categorical variables.
# Matplotlib allows you to pass categorical variables directly to
# many plotting functions. For example:
names = ['group_a', 'group_b', 'group_c']
values = [1, 10, 100]
plt.figure(1, figsize=(9, 3))
plt.subplot(131)
plt.bar(names, values)
plt.subplot(132)
plt.scatter(names, values)
plt.subplot(133)
plt.plot(names, values)
plt.suptitle('Categorical Plotting')
plt.show()
###############################################################################
# .. _controlling-line-properties:
#
# Controlling line properties
# ===========================
#
# Lines have many attributes that you can set: linewidth, dash style,
# antialiased, etc; see :class:`matplotlib.lines.Line2D`. There are
# several ways to set line properties
#
# * Use keyword args::
#
# plt.plot(x, y, linewidth=2.0)
#
#
# * Use the setter methods of a ``Line2D`` instance. ``plot`` returns a list
# of ``Line2D`` objects; e.g., ``line1, line2 = plot(x1, y1, x2, y2)``. In the code
# below we will suppose that we have only
# one line so that the list returned is of length 1. We use tuple unpacking with
# ``line,`` to get the first element of that list::
#
# line, = plt.plot(x, y, '-')
# line.set_antialiased(False) # turn off antialising
#
# * Use the :func:`~matplotlib.pyplot.setp` command. The example below
# uses a MATLAB-style command to set multiple properties
# on a list of lines. ``setp`` works transparently with a list of objects
# or a single object. You can either use python keyword arguments or
# MATLAB-style string/value pairs::
#
# lines = plt.plot(x1, y1, x2, y2)
# # use keyword args
# plt.setp(lines, color='r', linewidth=2.0)
# # or MATLAB style string value pairs
# plt.setp(lines, 'color', 'r', 'linewidth', 2.0)
#
#
# Here are the available :class:`~matplotlib.lines.Line2D` properties.
#
# ====================== ==================================================
# Property Value Type
# ====================== ==================================================
# alpha float
# animated [True | False]
# antialiased or aa [True | False]
# clip_box a matplotlib.transform.Bbox instance
# clip_on [True | False]
# clip_path a Path instance and a Transform instance, a Patch
# color or c any matplotlib color
# contains the hit testing function
# dash_capstyle [``'butt'`` | ``'round'`` | ``'projecting'``]
# dash_joinstyle [``'miter'`` | ``'round'`` | ``'bevel'``]
# dashes sequence of on/off ink in points
# data (np.array xdata, np.array ydata)
# figure a matplotlib.figure.Figure instance
# label any string
# linestyle or ls [ ``'-'`` | ``'--'`` | ``'-.'`` | ``':'`` | ``'steps'`` | ...]
# linewidth or lw float value in points
# lod [True | False]
# marker [ ``'+'`` | ``','`` | ``'.'`` | ``'1'`` | ``'2'`` | ``'3'`` | ``'4'`` ]
# markeredgecolor or mec any matplotlib color
# markeredgewidth or mew float value in points
# markerfacecolor or mfc any matplotlib color
# markersize or ms float
# markevery [ None | integer | (startind, stride) ]
# picker used in interactive line selection
# pickradius the line pick selection radius
# solid_capstyle [``'butt'`` | ``'round'`` | ``'projecting'``]
# solid_joinstyle [``'miter'`` | ``'round'`` | ``'bevel'``]
# transform a matplotlib.transforms.Transform instance
# visible [True | False]
# xdata np.array
# ydata np.array
# zorder any number
# ====================== ==================================================
#
# To get a list of settable line properties, call the
# :func:`~matplotlib.pyplot.setp` function with a line or lines
# as argument
#
# .. sourcecode:: ipython
#
# In [69]: lines = plt.plot([1, 2, 3])
#
# In [70]: plt.setp(lines)
# alpha: float
# animated: [True | False]
# antialiased or aa: [True | False]
# ...snip
#
# .. _multiple-figs-axes:
#
#
# Working with multiple figures and axes
# ======================================
#
# MATLAB, and :mod:`~matplotlib.pyplot`, have the concept of the current
# figure and the current axes. All plotting commands apply to the
# current axes. The function :func:`~matplotlib.pyplot.gca` returns the
# current axes (a :class:`matplotlib.axes.Axes` instance), and
# :func:`~matplotlib.pyplot.gcf` returns the current figure
# (:class:`matplotlib.figure.Figure` instance). Normally, you don't have
# to worry about this, because it is all taken care of behind the
# scenes. Below is a script to create two subplots.
def f(t):
return np.exp(-t) * np.cos(2*np.pi*t)
t1 = np.arange(0.0, 5.0, 0.1)
t2 = np.arange(0.0, 5.0, 0.02)
plt.figure(1)
plt.subplot(211)
plt.plot(t1, f(t1), 'bo', t2, f(t2), 'k')
plt.subplot(212)
plt.plot(t2, np.cos(2*np.pi*t2), 'r--')
plt.show()
###############################################################################
# The :func:`~matplotlib.pyplot.figure` command here is optional because
# ``figure(1)`` will be created by default, just as a ``subplot(111)``
# will be created by default if you don't manually specify any axes. The
# :func:`~matplotlib.pyplot.subplot` command specifies ``numrows,
# numcols, fignum`` where ``fignum`` ranges from 1 to
# ``numrows*numcols``. The commas in the ``subplot`` command are
# optional if ``numrows*numcols<10``. So ``subplot(211)`` is identical
# to ``subplot(2, 1, 1)``.
#
# You can create an arbitrary number of subplots
# and axes. If you want to place an axes manually, i.e., not on a
# rectangular grid, use the :func:`~matplotlib.pyplot.axes` command,
# which allows you to specify the location as ``axes([left, bottom,
# width, height])`` where all values are in fractional (0 to 1)
# coordinates. See :ref:`sphx_glr_gallery_pylab_examples_axes_demo.py` for an example of
# placing axes manually and :ref:`sphx_glr_gallery_subplots_axes_and_figures_subplot_demo.py` for an
# example with lots of subplots.
#
#
# You can create multiple figures by using multiple
# :func:`~matplotlib.pyplot.figure` calls with an increasing figure
# number. Of course, each figure can contain as many axes and subplots
# as your heart desires::
#
# import matplotlib.pyplot as plt
# plt.figure(1) # the first figure
# plt.subplot(211) # the first subplot in the first figure
# plt.plot([1, 2, 3])
# plt.subplot(212) # the second subplot in the first figure
# plt.plot([4, 5, 6])
#
#
# plt.figure(2) # a second figure
# plt.plot([4, 5, 6]) # creates a subplot(111) by default
#
# plt.figure(1) # figure 1 current; subplot(212) still current
# plt.subplot(211) # make subplot(211) in figure1 current
# plt.title('Easy as 1, 2, 3') # subplot 211 title
#
# You can clear the current figure with :func:`~matplotlib.pyplot.clf`
# and the current axes with :func:`~matplotlib.pyplot.cla`. If you find
# it annoying that states (specifically the current image, figure and axes)
# are being maintained for you behind the scenes, don't despair: this is just a thin
# stateful wrapper around an object oriented API, which you can use
# instead (see :ref:`sphx_glr_tutorials_02_intermediate_artists.py`)
#
# If you are making lots of figures, you need to be aware of one
# more thing: the memory required for a figure is not completely
# released until the figure is explicitly closed with
# :func:`~matplotlib.pyplot.close`. Deleting all references to the
# figure, and/or using the window manager to kill the window in which
# the figure appears on the screen, is not enough, because pyplot
# maintains internal references until :func:`~matplotlib.pyplot.close`
# is called.
#
# .. _working-with-text:
#
# Working with text
# =================
#
# The :func:`~matplotlib.pyplot.text` command can be used to add text in
# an arbitrary location, and the :func:`~matplotlib.pyplot.xlabel`,
# :func:`~matplotlib.pyplot.ylabel` and :func:`~matplotlib.pyplot.title`
# are used to add text in the indicated locations (see :ref:`sphx_glr_tutorials_text_text_intro.py`
# for a more detailed example)
mu, sigma = 100, 15
x = mu + sigma * np.random.randn(10000)
# the histogram of the data
n, bins, patches = plt.hist(x, 50, normed=1, facecolor='g', alpha=0.75)
plt.xlabel('Smarts')
plt.ylabel('Probability')
plt.title('Histogram of IQ')
plt.text(60, .025, r'$\mu=100,\ \sigma=15$')
plt.axis([40, 160, 0, 0.03])
plt.grid(True)
plt.show()
###############################################################################
# All of the :func:`~matplotlib.pyplot.text` commands return an
# :class:`matplotlib.text.Text` instance. Just as with with lines
# above, you can customize the properties by passing keyword arguments
# into the text functions or using :func:`~matplotlib.pyplot.setp`::
#
# t = plt.xlabel('my data', fontsize=14, color='red')
#
# These properties are covered in more detail in :ref:`sphx_glr_tutorials_text_text_props.py`.
#
#
# Using mathematical expressions in text
# --------------------------------------
#
# matplotlib accepts TeX equation expressions in any text expression.
# For example to write the expression :math:`\sigma_i=15` in the title,
# you can write a TeX expression surrounded by dollar signs::
#
# plt.title(r'$\sigma_i=15$')
#
# The ``r`` preceding the title string is important -- it signifies
# that the string is a *raw* string and not to treat backslashes as
# python escapes. matplotlib has a built-in TeX expression parser and
# layout engine, and ships its own math fonts -- for details see
# :ref:`sphx_glr_tutorials_text_mathtext.py`. Thus you can use mathematical text across platforms
# without requiring a TeX installation. For those who have LaTeX and
# dvipng installed, you can also use LaTeX to format your text and
# incorporate the output directly into your display figures or saved
# postscript -- see :ref:`sphx_glr_tutorials_text_usetex.py`.
#
#
# Annotating text
# ---------------
#
# The uses of the basic :func:`~matplotlib.pyplot.text` command above
# place text at an arbitrary position on the Axes. A common use for
# text is to annotate some feature of the plot, and the
# :func:`~matplotlib.pyplot.annotate` method provides helper
# functionality to make annotations easy. In an annotation, there are
# two points to consider: the location being annotated represented by
# the argument ``xy`` and the location of the text ``xytext``. Both of
# these arguments are ``(x,y)`` tuples.
ax = plt.subplot(111)
t = np.arange(0.0, 5.0, 0.01)
s = np.cos(2*np.pi*t)
line, = plt.plot(t, s, lw=2)
plt.annotate('local max', xy=(2, 1), xytext=(3, 1.5),
arrowprops=dict(facecolor='black', shrink=0.05),
)
plt.ylim(-2, 2)
plt.show()
###############################################################################
# In this basic example, both the ``xy`` (arrow tip) and ``xytext``
# locations (text location) are in data coordinates. There are a
# variety of other coordinate systems one can choose -- see
# :ref:`annotations-tutorial` and :ref:`plotting-guide-annotation` for
# details. More examples can be found in
# :ref:`sphx_glr_gallery_text_labels_and_annotations_annotation_demo.py`.
#
#
# Logarithmic and other nonlinear axes
# ====================================
#
# :mod:`matplotlib.pyplot` supports not only linear axis scales, but also
# logarithmic and logit scales. This is commonly used if data spans many orders
# of magnitude. Changing the scale of an axis is easy:
#
# plt.xscale('log')
#
# An example of four plots with the same data and different scales for the y axis
# is shown below.
from matplotlib.ticker import NullFormatter # useful for `logit` scale
# Fixing random state for reproducibility
np.random.seed(19680801)
# make up some data in the interval ]0, 1[
y = np.random.normal(loc=0.5, scale=0.4, size=1000)
y = y[(y > 0) & (y < 1)]
y.sort()
x = np.arange(len(y))
# plot with various axes scales
plt.figure(1)
# linear
plt.subplot(221)
plt.plot(x, y)
plt.yscale('linear')
plt.title('linear')
plt.grid(True)
# log
plt.subplot(222)
plt.plot(x, y)
plt.yscale('log')
plt.title('log')
plt.grid(True)
# symmetric log
plt.subplot(223)
plt.plot(x, y - y.mean())
plt.yscale('symlog', linthreshy=0.01)
plt.title('symlog')
plt.grid(True)
# logit
plt.subplot(224)
plt.plot(x, y)
plt.yscale('logit')
plt.title('logit')
plt.grid(True)
# Format the minor tick labels of the y-axis into empty strings with
# `NullFormatter`, to avoid cumbering the axis with too many labels.
plt.gca().yaxis.set_minor_formatter(NullFormatter())
# Adjust the subplot layout, because the logit one may take more space
# than usual, due to y-tick labels like "1 - 10^{-3}"
plt.subplots_adjust(top=0.92, bottom=0.08, left=0.10, right=0.95, hspace=0.25,
wspace=0.35)
plt.show()
###############################################################################
# It is also possible to add your own scale, see :ref:`adding-new-scales` for
# details.