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

    Click :ref:`here <sphx_glr_download_gallery_misc_histogram_path.py>` to download the full example code
.. rst-class:: sphx-glr-example-title

.. _sphx_glr_gallery_misc_histogram_path.py:


========================================================
Building histograms using Rectangles and PolyCollections
========================================================

Using a path patch to draw rectangles.
The technique of using lots of Rectangle instances, or
the faster method of using PolyCollections, were implemented before we
had proper paths with moveto/lineto, closepoly etc in mpl.  Now that
we have them, we can draw collections of regularly shaped objects with
homogeneous properties more efficiently with a PathCollection. This
example makes a histogram -- it's more work to set up the vertex arrays
at the outset, but it should be much faster for large numbers of
objects.



.. code-block:: python


    import numpy as np
    import matplotlib.pyplot as plt
    import matplotlib.patches as patches
    import matplotlib.path as path

    fig, ax = plt.subplots()

    # Fixing random state for reproducibility
    np.random.seed(19680801)


    # histogram our data with numpy

    data = np.random.randn(1000)
    n, bins = np.histogram(data, 50)

    # 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


    # we need a (numrects x numsides x 2) numpy array for the path helper
    # function to build a compound path
    XY = np.array([[left, left, right, right], [bottom, top, top, bottom]]).T

    # get the Path object
    barpath = path.Path.make_compound_path_from_polys(XY)

    # make a patch out of it
    patch = patches.PathPatch(barpath)
    ax.add_patch(patch)

    # update the view limits
    ax.set_xlim(left[0], right[-1])
    ax.set_ylim(bottom.min(), top.max())

    plt.show()




.. image:: /gallery/misc/images/sphx_glr_histogram_path_001.png
    :class: sphx-glr-single-img




It should be noted that instead of creating a three-dimensional array and
using `~.path.Path.make_compound_path_from_polys`, we could as well create
the compound path directly using vertices and codes as shown below



.. code-block:: python


    nrects = len(left)
    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

    barpath = path.Path(verts, codes)







------------

References
""""""""""

The use of the following functions, methods, classes and modules is shown
in this example:



.. code-block:: python


    import matplotlib
    matplotlib.patches
    matplotlib.patches.PathPatch
    matplotlib.path
    matplotlib.path.Path
    matplotlib.path.Path.make_compound_path_from_polys
    matplotlib.axes.Axes.add_patch
    matplotlib.collections.PathCollection

    # This example shows an alternative to
    matplotlib.collections.PolyCollection
    matplotlib.axes.Axes.hist







.. _sphx_glr_download_gallery_misc_histogram_path.py:


.. only :: html

 .. container:: sphx-glr-footer
    :class: sphx-glr-footer-example



  .. container:: sphx-glr-download

     :download:`Download Python source code: histogram_path.py <histogram_path.py>`



  .. container:: sphx-glr-download

     :download:`Download Jupyter notebook: histogram_path.ipynb <histogram_path.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>`_
