to achieve the desired plot::

.. _annotations-tutorial:

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 case of

text is to annotate some feature of the plot, and the

:func:`~matplotlib.Axes.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.

.. literalinclude:: figures/annotation_basic.py

.. image:: figures/annotation_basic.png

:scale: 50

In this 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 -- you can specify the coordinate

system of ``xy`` and ``xytext`` with one of the following strings for

``xycoords`` and ``textcoords`` (default is 'data')

argument coordinate system

'figure points' points from the lower left corner of the figure

'figure pixels' pixels from the lower left corner of the figure

'figure fraction' 0,0 is lower left of figure and 1,1 is upper, right

'axes points' points from lower left corner of axes

'axes pixels' pixels from lower left corner of axes

'axes fraction' 0,1 is lower left of axes and 1,1 is upper right

'data' use the axes data coordinate system

For example to place the text coordinates in fractional axes

coordinates, one could do::

For physical coordinate systems (points or pixels) the origin is the

(bottom, left) of the figure or axes. If the value is negative,

however, the origin is from the (right, top) of the figure or axes,

analogous to negative indexing of sequences.

Optionally, you can specify arrow properties which draws an arrow

from the text to the annotated point by giving a dictionary of arrow

properties in the optional keyword argument ``arrowprops``.

``arrowprops`` key description

width the width of the arrow in points

frac the fraction of the arrow length occupied by the head

headwidth the width of the base of the arrow head in points

shrink move the tip and base some percent away from the annotated point and text

\*\*kwargs any key for :class:`matplotlib.patches.Polygon`, eg ``facecolor``

In the example below, the ``xy`` point is in native coordinates

(``xycoords`` defaults to 'data'). For a polar axes, this is in

(theta, radius) space. The text in this example is placed in the

fractional figure coordinate system. :class:`matplotlib.text.Text`

keyword args like ``horizontalalignment``, ``verticalalignment`` and

``fontsize are passed from the `~matplotlib.Axes.annotate` to the

``Text`` instance

.. literalinclude:: figures/annotation_polar.py

.. image:: figures/annotation_polar.png

:scale: 50

See the `annotations demo

<http://matplotlib.sf.net/examples/pylab_examples/annotation_demo.py>`_ for more

examples.

Event handling and picking

import numpy as np

import matplotlib.pyplot as plt

fig = plt.figure()

ax = fig.add_subplot(111)

t = np.arange(0.0, 5.0, 0.01)

s = np.cos(2*np.pi*t)

line, = ax.plot(t, s, lw=2)

ax.annotate('local max', xy=(2, 1), xytext=(3, 1.5),

arrowprops=dict(facecolor='black', shrink=0.05),

)

ax.set_ylim(-2,2)

plt.show()

import numpy as np

import matplotlib.pyplot as plt

fig = plt.figure()

ax = fig.add_subplot(111, polar=True)

r = np.arange(0,1,0.001)

theta = 2*2*np.pi*r

line, = ax.plot(theta, r, color='#ee8d18', lw=3)

ind = 800

thisr, thistheta = r[ind], theta[ind]

ax.plot([thistheta], [thisr], 'o')

ax.annotate('a polar annotation',

xy=(thistheta, thisr), # theta, radius

xytext=(0.05, 0.05), # fraction, fraction

textcoords='figure fraction',

arrowprops=dict(facecolor='black', shrink=0.05),

horizontalalignment='left',

verticalalignment='bottom',

)

plt.show()

import numpy as np

import matplotlib.pyplot as plt

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()

index_text.rst

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::

The ``r`` preceeding the title string is important -- it signifies

that the string is a *raw* string and not to treate backslashes and

python escapes. matplotlib has a built-in TeX expression parser and

layout engine, and ships its own math fonts -- for details see

:ref:`mathtext-tutorial`. 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:`usetex-tutorial`.

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 case of

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.

.. literalinclude:: figures/pyplot_annotate.py

.. image:: figures/pyplot_annotate.png

:scale: 50

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` for details. More examples can be found

in the `annotations demo

<http://matplotlib.sf.net/examples/pylab_examples/annotation_demo.py>`_

Text rendering With LaTeX