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DOC: fix levels in user/explain/figure #26110

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187 changes: 187 additions & 0 deletions galleries/users_explain/artists/artist_intro.rst
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.. _users_artists:

Introduction to Artists
-----------------------

Almost all objects you interact with on a Matplotlib plot are called "Artist"
(and are subclasses of the `.Artist` class). :doc:`Figure <../figure/index>`
and :doc:`Axes <../axes/index>` are Artists, and generally contain :doc:`Axis
<../axis/index>` Artists and Artists that contain data or annotation
information.
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Almost all objects you interact with on a Matplotlib plot are called "Artist"
(and are subclasses of the `.Artist` class). :doc:`Figure <../figure/index>`
and :doc:`Axes <../axes/index>` are Artists, and generally contain :doc:`Axis
<../axis/index>` Artists and Artists that contain data or annotation
information.
Artist and ArtistLike objects store information on how visual elements in a figure look and behave and pass this information to a renderer. Most parts of the image are generated via subclasses of `.Artist` and these objects may be nested. For example a :doc:`Figure <../figure/index>` artist can contain multiple :doc:`Axes <../axes/index>` that each contain multiple :doc:`Axis <../axis/index>`.

I think stealing the language of the API docs makes for a softer intro https://matplotlib.org/devdocs/api/artist_api.html#module-matplotlib.artist



Creating Artists
~~~~~~~~~~~~~~~~

Usually we do not instantiate Artists directly, but rather use a plotting
method on `~.axes.Axes`. Some examples of plotting methods and the Artist
object they create is given below:
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object they create is given below:
object they create are given below:


========================================= =================
Axes helper method Artist
========================================= =================
`~.axes.Axes.annotate` - text annotations `.Annotation`
`~.axes.Axes.bar` - bar charts `.Rectangle`
`~.axes.Axes.errorbar` - error bar plots `.Line2D` and
`.Rectangle`
`~.axes.Axes.fill` - shared area `.Polygon`
`~.axes.Axes.hist` - histograms `.Rectangle`
`~.axes.Axes.imshow` - image data `.AxesImage`
`~.axes.Axes.legend` - Axes legend `.Legend`
`~.axes.Axes.plot` - xy plots `.Line2D`
`~.axes.Axes.scatter` - scatter charts `.PolyCollection`
`~.axes.Axes.text` - text `.Text`
========================================= =================

As an example, we can save the Line2D Artist returned from `.axes.Axes.plot`:

.. sourcecode:: ipython

In [209]: import matplotlib.pyplot as plt
In [210]: import matplotlib.artist as martist
In [211]: import numpy as np

In [212]: fig, ax = plt.subplots()
In [213]: x, y = np.random.rand(2, 100)
In [214]: lines = ax.plot(x, y, '-', label='example')
In [215]: print(lines)
[<matplotlib.lines.Line2D at 0xd378b0c>]

Note that ``plot`` returns a _list_ of lines because you can pass in multiple x,
y pairs to plot. The line has been added to the Axes, and we can retrieve the
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Note that ``plot`` returns a _list_ of lines because you can pass in multiple x,
y pairs to plot. The line has been added to the Axes, and we can retrieve the
Note that ``plot`` returns a _list_ of lines because it generates multiple line plots when given multiple x,y pairs as input. The line has been added to the Axes, and we can retrieve the

little nit to tie return more closely to the visual generated

Artist via `~.Axes.get_lines()`:

.. sourcecode:: ipython

In [216]: print(ax.get_lines())
<a list of 1 Line2D objects>
In [217]: print(ax.get_lines()[0])
Line2D(example)

Changing Artist properties
~~~~~~~~~~~~~~~~~~~~~~~~~~

Getting the ``lines`` object gives us access to all the properties of the
Line2D object. So if we want to change the *linewidth* after the fact, we can do so using `.Artist.set`.
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Line2D object. So if we want to change the *linewidth* after the fact, we can do so using `.Artist.set`.
Line2D object. If we want to change the *linewidth* after the fact, we can do so using `.Artist.set`.


.. plot::
:include-source:

fig, ax = plt.subplots(figsize=(4, 2.5))
x = np.arange(0, 13, 0.2)
y = np.sin(x)
lines = ax.plot(x, y, '-', label='example', linewidth=0.2, color='blue')
lines[0].set(color='green', linewidth=2)

We can interrogate the full list of settable properties with
`matplotlib.artist.getp`:
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Suggested change
We can interrogate the full list of settable properties with
`matplotlib.artist.getp`:
`matplotlib.artist.getp` returns the full list of settable properties:


.. sourcecode:: ipython

In [218]: martist.getp(lines[0])
agg_filter = None
alpha = None
animated = False
antialiased or aa = True
bbox = Bbox(x0=0.004013842290585101, y0=0.013914221641967...
children = []
clip_box = TransformedBbox( Bbox(x0=0.0, y0=0.0, x1=1.0, ...
clip_on = True
clip_path = None
color or c = blue
dash_capstyle = butt
dash_joinstyle = round
data = (array([0.91377845, 0.58456834, 0.36492019, 0.0379...
drawstyle or ds = default
figure = Figure(550x450)
fillstyle = full
gapcolor = None
gid = None
in_layout = True
label = example
linestyle or ls = -
linewidth or lw = 2.0
marker = None
markeredgecolor or mec = blue
markeredgewidth or mew = 1.0
markerfacecolor or mfc = blue
markerfacecoloralt or mfcalt = none
markersize or ms = 6.0
markevery = None
mouseover = False
path = Path(array([[0.91377845, 0.51224793], [0.58...
path_effects = []
picker = None
pickradius = 5
rasterized = False
sketch_params = None
snap = None
solid_capstyle = projecting
solid_joinstyle = round
tightbbox = Bbox(x0=70.4609002763619, y0=54.321277798941786, x...
transform = CompositeGenericTransform( TransformWrapper( ...
transformed_clip_path_and_affine = (None, None)
url = None
visible = True
window_extent = Bbox(x0=70.4609002763619, y0=54.321277798941786, x...
xdata = [0.91377845 0.58456834 0.36492019 0.03796664 0.884...
xydata = [[0.91377845 0.51224793] [0.58456834 0.9820474 ] ...
ydata = [0.51224793 0.9820474 0.24469912 0.61647032 0.483...
zorder = 2

Note most Artists also have a distinct list of setters; e.g.
`.Line2D.set_color` or `.Line2D.set_linewidth`.

Changing Artist data
~~~~~~~~~~~~~~~~~~~~

In addition to styling properties like *color* and *linewidth*, the Line2D
object has a *data* property. You can set the data after the line has been
created using `.Line2D.set_data`. This is often used for Animations, where the
same line is shown evolving over time (see :doc:`../animations/index`)

.. plot::
:include-source:

fig, ax = plt.subplots(figsize=(4, 2.5))
x = np.arange(0, 13, 0.2)
y = np.sin(x)
lines = ax.plot(x, y, '-', label='example')
lines[0].set_data([x, np.cos(x)])

Manually adding Artists
~~~~~~~~~~~~~~~~~~~~~~~

Not all Artists have helper methods, or you may want to use a low-level method
for some reason. For example the `.patches.Circle` Artist does not have a
helper, but we can still create and add to an Axes using the
`.axes.Axes.add_artist` method:
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Suggested change
Not all Artists have helper methods, or you may want to use a low-level method
for some reason. For example the `.patches.Circle` Artist does not have a
helper, but we can still create and add to an Axes using the
`.axes.Axes.add_artist` method:
Any artist object can be manually added to an Axes using the `.axes.Axes.add_artist` method:

It's unclear what helper method means in this context so I think it makes more sense to just be direct.


.. plot::
:include-source:

import matplotlib.patches as mpatches

fig, ax = plt.subplots(figsize=(4, 2.5))
circle = mpatches.Circle((0.5, 0.5), 0.25, ec="none")
ax.add_artist(circle)
clipped_circle = mpatches.Circle((1, 0.5), 0.125, ec="none", facecolor='C1')
ax.add_artist(clipped_circle)
ax.set_aspect(1)

The Circle takes the center and radius of the Circle as arguments to its
constructor; optional arguments are passed as keyword arguments.

Note that when we add an Artist manually like this, it doesn't necessarily
adjust the axis limits like most of the helper methods do, so the Artists can
be clipped, as is the case above for the ``clipped_circle`` patch.
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If clipping is important than it should be its own section


See :ref:`artist_reference` for other patches.

Removing Artists
~~~~~~~~~~~~~~~~

Sometimes we want to remove an Artist from a figure without re-specifying the
whole figure from scratch. Most Artists have a usable *remove* method that
will remove the Artist from its Axes list. For instance ``lines[0].remove()``
would remove the *Line2D* artist created in the example above.
198 changes: 11 additions & 187 deletions galleries/users_explain/artists/index.rst
View file
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Original file line number Diff line number Diff line change
@@ -1,200 +1,24 @@
.. _users_artists:

Using Artists
-------------
+++++++
Artists
+++++++

Almost all objects you interact with on a Matplotlib plot are called "Artist"
(and are subclasses of the `.Artist` class). :doc:`Figure <../figure/index>`
and :doc:`Axes <../axes/index>` are Artists, and generally contain :doc:`Axis
<../axis/index>` Artists and Artists that contain data or annotation
information.

.. toctree::
:maxdepth: 2

Creating Artists
~~~~~~~~~~~~~~~~

Usually we do not instantiate Artists directly, but rather use a plotting
method on `~.axes.Axes`. Some examples of plotting methods and the Artist
object they create is given below:

========================================= =================
Axes helper method Artist
========================================= =================
`~.axes.Axes.annotate` - text annotations `.Annotation`
`~.axes.Axes.bar` - bar charts `.Rectangle`
`~.axes.Axes.errorbar` - error bar plots `.Line2D` and
`.Rectangle`
`~.axes.Axes.fill` - shared area `.Polygon`
`~.axes.Axes.hist` - histograms `.Rectangle`
`~.axes.Axes.imshow` - image data `.AxesImage`
`~.axes.Axes.legend` - Axes legend `.Legend`
`~.axes.Axes.plot` - xy plots `.Line2D`
`~.axes.Axes.scatter` - scatter charts `.PolyCollection`
`~.axes.Axes.text` - text `.Text`
========================================= =================

As an example, we can save the Line2D Artist returned from `.axes.Axes.plot`:

.. sourcecode:: ipython

In [209]: import matplotlib.pyplot as plt
In [210]: import matplotlib.artist as martist
In [211]: import numpy as np

In [212]: fig, ax = plt.subplots()
In [213]: x, y = np.random.rand(2, 100)
In [214]: lines = ax.plot(x, y, '-', label='example')
In [215]: print(lines)
[<matplotlib.lines.Line2D at 0xd378b0c>]

Note that ``plot`` returns a _list_ of lines because you can pass in multiple x,
y pairs to plot. The line has been added to the Axes, and we can retrieve the
Artist via `~.Axes.get_lines()`:

.. sourcecode:: ipython

In [216]: print(ax.get_lines())
<a list of 1 Line2D objects>
In [217]: print(ax.get_lines()[0])
Line2D(example)

Changing Artist properties
~~~~~~~~~~~~~~~~~~~~~~~~~~

Getting the ``lines`` object gives us access to all the properties of the
Line2D object. So if we want to change the *linewidth* after the fact, we can do so using `.Artist.set`.

.. plot::
:include-source:

fig, ax = plt.subplots(figsize=(4, 2.5))
x = np.arange(0, 13, 0.2)
y = np.sin(x)
lines = ax.plot(x, y, '-', label='example', linewidth=0.2, color='blue')
lines[0].set(color='green', linewidth=2)

We can interrogate the full list of settable properties with
`matplotlib.artist.getp`:

.. sourcecode:: ipython

In [218]: martist.getp(lines[0])
agg_filter = None
alpha = None
animated = False
antialiased or aa = True
bbox = Bbox(x0=0.004013842290585101, y0=0.013914221641967...
children = []
clip_box = TransformedBbox( Bbox(x0=0.0, y0=0.0, x1=1.0, ...
clip_on = True
clip_path = None
color or c = blue
dash_capstyle = butt
dash_joinstyle = round
data = (array([0.91377845, 0.58456834, 0.36492019, 0.0379...
drawstyle or ds = default
figure = Figure(550x450)
fillstyle = full
gapcolor = None
gid = None
in_layout = True
label = example
linestyle or ls = -
linewidth or lw = 2.0
marker = None
markeredgecolor or mec = blue
markeredgewidth or mew = 1.0
markerfacecolor or mfc = blue
markerfacecoloralt or mfcalt = none
markersize or ms = 6.0
markevery = None
mouseover = False
path = Path(array([[0.91377845, 0.51224793], [0.58...
path_effects = []
picker = None
pickradius = 5
rasterized = False
sketch_params = None
snap = None
solid_capstyle = projecting
solid_joinstyle = round
tightbbox = Bbox(x0=70.4609002763619, y0=54.321277798941786, x...
transform = CompositeGenericTransform( TransformWrapper( ...
transformed_clip_path_and_affine = (None, None)
url = None
visible = True
window_extent = Bbox(x0=70.4609002763619, y0=54.321277798941786, x...
xdata = [0.91377845 0.58456834 0.36492019 0.03796664 0.884...
xydata = [[0.91377845 0.51224793] [0.58456834 0.9820474 ] ...
ydata = [0.51224793 0.9820474 0.24469912 0.61647032 0.483...
zorder = 2

Note most Artists also have a distinct list of setters; e.g.
`.Line2D.set_color` or `.Line2D.set_linewidth`.

Changing Artist data
~~~~~~~~~~~~~~~~~~~~

In addition to styling properties like *color* and *linewidth*, the Line2D
object has a *data* property. You can set the data after the line has been
created using `.Line2D.set_data`. This is often used for Animations, where the
same line is shown evolving over time (see :doc:`../animations/index`)

.. plot::
:include-source:

fig, ax = plt.subplots(figsize=(4, 2.5))
x = np.arange(0, 13, 0.2)
y = np.sin(x)
lines = ax.plot(x, y, '-', label='example')
lines[0].set_data([x, np.cos(x)])

Manually adding Artists
~~~~~~~~~~~~~~~~~~~~~~~

Not all Artists have helper methods, or you may want to use a low-level method
for some reason. For example the `.patches.Circle` Artist does not have a
helper, but we can still create and add to an Axes using the
`.axes.Axes.add_artist` method:

.. plot::
:include-source:

import matplotlib.patches as mpatches

fig, ax = plt.subplots(figsize=(4, 2.5))
circle = mpatches.Circle((0.5, 0.5), 0.25, ec="none")
ax.add_artist(circle)
clipped_circle = mpatches.Circle((1, 0.5), 0.125, ec="none", facecolor='C1')
ax.add_artist(clipped_circle)
ax.set_aspect(1)

The Circle takes the center and radius of the Circle as arguments to its
constructor; optional arguments are passed as keyword arguments.

Note that when we add an Artist manually like this, it doesn't necessarily
adjust the axis limits like most of the helper methods do, so the Artists can
be clipped, as is the case above for the ``clipped_circle`` patch.

See :ref:`artist_reference` for other patches.

Removing Artists
~~~~~~~~~~~~~~~~

Sometimes we want to remove an Artist from a figure without re-specifying the
whole figure from scratch. Most Artists have a usable *remove* method that
will remove the Artist from its Axes list. For instance ``lines[0].remove()``
would remove the *Line2D* artist created in the example above.

More details
~~~~~~~~~~~~
artist_intro

.. toctree::
:maxdepth: 1

Concept: Automated color cycle <color_cycle>
Concept: optimizing Artists for performance <performance>
Concept: Paths <paths>
Concept: Path effects guide <patheffects_guide>
In Depth: understanding the extent keyword argument of imshow <imshow_extent>
Automated color cycle <color_cycle>
Optimizing Artists for performance <performance>
Paths <paths>
Path effects guide <patheffects_guide>
Understanding the extent keyword argument of imshow <imshow_extent>
transforms_tutorial
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