.. note::
    :class: sphx-glr-download-link-note

    Click :ref:`here <sphx_glr_download_gallery_animation_animated_histogram.py>` 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 <animated_histogram.py>`



  .. container:: sphx-glr-download

     :download:`Download Jupyter notebook: animated_histogram.ipynb <animated_histogram.ipynb>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    Keywords: matplotlib code example, codex, python plot, pyplot
    `Gallery generated by Sphinx-Gallery
    <https://sphinx-gallery.readthedocs.io>`_
