.. _sphx_glr_gallery_showcase_integral.py:


==================================
Integral as the area under a curve
==================================

Although this is a simple example, it demonstrates some important tweaks:

    * A simple line plot with custom color and line width.
    * A shaded region created using a Polygon patch.
    * A text label with mathtext rendering.
    * figtext calls to label the x- and y-axes.
    * Use of axis spines to hide the top and right spines.
    * Custom tick placement and labels.




.. image:: /gallery/showcase/images/sphx_glr_integral_001.png
    :align: center





.. code-block:: python

    import numpy as np
    import matplotlib.pyplot as plt
    from matplotlib.patches import Polygon


    def func(x):
        return (x - 3) * (x - 5) * (x - 7) + 85


    a, b = 2, 9  # integral limits
    x = np.linspace(0, 10)
    y = func(x)

    fig, ax = plt.subplots()
    plt.plot(x, y, 'r', linewidth=2)
    plt.ylim(ymin=0)

    # Make the shaded region
    ix = np.linspace(a, b)
    iy = func(ix)
    verts = [(a, 0)] + list(zip(ix, iy)) + [(b, 0)]
    poly = Polygon(verts, facecolor='0.9', edgecolor='0.5')
    ax.add_patch(poly)

    plt.text(0.5 * (a + b), 30, r"$\int_a^b f(x)\mathrm{d}x$",
             horizontalalignment='center', fontsize=20)

    plt.figtext(0.9, 0.05, '$x$')
    plt.figtext(0.1, 0.9, '$y$')

    ax.spines['right'].set_visible(False)
    ax.spines['top'].set_visible(False)
    ax.xaxis.set_ticks_position('bottom')

    ax.set_xticks((a, b))
    ax.set_xticklabels(('$a$', '$b$'))
    ax.set_yticks([])

    plt.show()



.. only :: html

 .. container:: sphx-glr-footer


  .. container:: sphx-glr-download

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



  .. container:: sphx-glr-download

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


.. only:: html

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

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.readthedocs.io>`_