.. note::
:class: sphx-glr-download-link-note
Click :ref:`here ` to download the full example code
.. rst-class:: sphx-glr-example-title
.. _sphx_glr_gallery_animation_animated_histogram.py:
==================
Animated histogram
==================
Use a path patch to draw a bunch of rectangles for an animated histogram.
.. code-block:: python
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as patches
import matplotlib.path as path
import matplotlib.animation as animation
# Fixing random state for reproducibility
np.random.seed(19680801)
# histogram our data with numpy
data = np.random.randn(1000)
n, bins = np.histogram(data, 100)
# get the corners of the rectangles for the histogram
left = np.array(bins[:-1])
right = np.array(bins[1:])
bottom = np.zeros(len(left))
top = bottom + n
nrects = len(left)
Here comes the tricky part -- we have to set up the vertex and path codes
arrays using ``plt.Path.MOVETO``, ``plt.Path.LINETO`` and
``plt.Path.CLOSEPOLY`` for each rect.
* We need 1 ``MOVETO`` per rectangle, which sets the initial point.
* We need 3 ``LINETO``'s, which tell Matplotlib to draw lines from
vertex 1 to vertex 2, v2 to v3, and v3 to v4.
* We then need one ``CLOSEPOLY`` which tells Matplotlib to draw a line from
the v4 to our initial vertex (the ``MOVETO`` vertex), in order to close the
polygon.
.. note::
The vertex for ``CLOSEPOLY`` is ignored, but we still need a placeholder
in the ``verts`` array to keep the codes aligned with the vertices.
.. code-block:: python
nverts = nrects * (1 + 3 + 1)
verts = np.zeros((nverts, 2))
codes = np.ones(nverts, int) * path.Path.LINETO
codes[0::5] = path.Path.MOVETO
codes[4::5] = path.Path.CLOSEPOLY
verts[0::5, 0] = left
verts[0::5, 1] = bottom
verts[1::5, 0] = left
verts[1::5, 1] = top
verts[2::5, 0] = right
verts[2::5, 1] = top
verts[3::5, 0] = right
verts[3::5, 1] = bottom
To animate the histogram, we need an ``animate`` function, which generates
a random set of numbers and updates the locations of the vertices for the
histogram (in this case, only the heights of each rectangle). ``patch`` will
eventually be a ``Patch`` object.
.. code-block:: python
patch = None
def animate(i):
# simulate new data coming in
data = np.random.randn(1000)
n, bins = np.histogram(data, 100)
top = bottom + n
verts[1::5, 1] = top
verts[2::5, 1] = top
return [patch, ]
And now we build the `Path` and `Patch` instances for the histogram using
our vertices and codes. We add the patch to the `Axes` instance, and setup
the `FuncAnimation` with our animate function.
.. code-block:: python
fig, ax = plt.subplots()
barpath = path.Path(verts, codes)
patch = patches.PathPatch(
barpath, facecolor='green', edgecolor='yellow', alpha=0.5)
ax.add_patch(patch)
ax.set_xlim(left[0], right[-1])
ax.set_ylim(bottom.min(), top.max())
ani = animation.FuncAnimation(fig, animate, 100, repeat=False, blit=True)
plt.show()
.. image:: /gallery/animation/images/sphx_glr_animated_histogram_001.png
:class: sphx-glr-single-img
.. _sphx_glr_download_gallery_animation_animated_histogram.py:
.. only :: html
.. container:: sphx-glr-footer
:class: sphx-glr-footer-example
.. container:: sphx-glr-download
:download:`Download Python source code: animated_histogram.py `
.. container:: sphx-glr-download
:download:`Download Jupyter notebook: animated_histogram.ipynb `
.. only:: html
.. rst-class:: sphx-glr-signature
Keywords: matplotlib code example, codex, python plot, pyplot
`Gallery generated by Sphinx-Gallery
`_