

.. _sphx_glr_gallery_lines_bars_and_markers_multicolored_line.py:


==================
Multicolored lines
==================

This example shows how to make a multi-colored line. In this example, the line
is colored based on its derivative.




.. image:: /gallery/lines_bars_and_markers/images/sphx_glr_multicolored_line_001.png
    :align: center





.. code-block:: python


    import numpy as np
    import matplotlib.pyplot as plt
    from matplotlib.collections import LineCollection
    from matplotlib.colors import ListedColormap, BoundaryNorm

    x = np.linspace(0, 3 * np.pi, 500)
    y = np.sin(x)
    dydx = np.cos(0.5 * (x[:-1] + x[1:]))  # first derivative

    # Create a set of line segments so that we can color them individually
    # This creates the points as a N x 1 x 2 array so that we can stack points
    # together easily to get the segments. The segments array for line collection
    # needs to be (numlines) x (points per line) x 2 (for x and y)
    points = np.array([x, y]).T.reshape(-1, 1, 2)
    segments = np.concatenate([points[:-1], points[1:]], axis=1)

    fig, axs = plt.subplots(2, 1, sharex=True, sharey=True)

    # Create a continuous norm to map from data points to colors
    norm = plt.Normalize(dydx.min(), dydx.max())
    lc = LineCollection(segments, cmap='viridis', norm=norm)
    # Set the values used for colormapping
    lc.set_array(dydx)
    lc.set_linewidth(2)
    line = axs[0].add_collection(lc)
    fig.colorbar(line, ax=axs[0])

    # Use a boundary norm instead
    cmap = ListedColormap(['r', 'g', 'b'])
    norm = BoundaryNorm([-1, -0.5, 0.5, 1], cmap.N)
    lc = LineCollection(segments, cmap=cmap, norm=norm)
    lc.set_array(dydx)
    lc.set_linewidth(2)
    line = axs[1].add_collection(lc)
    fig.colorbar(line, ax=axs[1])

    axs[0].set_xlim(x.min(), x.max())
    axs[0].set_ylim(-1.1, 1.1)
    plt.show()

**Total running time of the script:** ( 0 minutes  0.164 seconds)



.. container:: sphx-glr-footer


  .. container:: sphx-glr-download

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



  .. container:: sphx-glr-download

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

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

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