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

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

.. _sphx_glr_gallery_lines_bars_and_markers_markevery_demo.py:


==============
Markevery Demo
==============

This example demonstrates the various options for showing a marker at a
subset of data points using the ``markevery`` property of a Line2D object.

Integer arguments are fairly intuitive.  e.g. ``markevery=5`` will plot every
5th marker starting from the first data point.

Float arguments allow markers to be spaced at approximately equal distances
along the line.  The theoretical distance along the line between markers is
determined by multiplying the display-coordinate distance of the axes
bounding-box diagonal by the value of ``markevery``.  The data points closest
to the theoretical distances will be shown.

A slice or list/array can also be used with ``markevery`` to specify the
markers to show.


.. code-block:: python


    import numpy as np
    import matplotlib.pyplot as plt
    import matplotlib.gridspec as gridspec

    # define a list of markevery cases to plot
    cases = [None,
             8,
             (30, 8),
             [16, 24, 30], [0, -1],
             slice(100, 200, 3),
             0.1, 0.3, 1.5,
             (0.0, 0.1), (0.45, 0.1)]

    # define the figure size and grid layout properties
    figsize = (10, 8)
    cols = 3
    rows = len(cases) // cols + 1
    # define the data for cartesian plots
    delta = 0.11
    x = np.linspace(0, 10 - 2 * delta, 200) + delta
    y = np.sin(x) + 1.0 + delta


    def trim_axs(axs, N):
        """little helper to massage the axs list to have correct length..."""
        axs = axs.flat
        for ax in axs[N:]:
            ax.remove()
        return axs[:N]







Plot each markevery case for linear x and y scales



.. code-block:: python


    fig1, axs = plt.subplots(rows, cols, figsize=figsize, constrained_layout=True)
    axs = trim_axs(axs, len(cases))
    for ax, case in zip(axs, cases):
        ax.set_title('markevery=%s' % str(case))
        ax.plot(x, y, 'o', ls='-', ms=4, markevery=case)




.. image:: /gallery/lines_bars_and_markers/images/sphx_glr_markevery_demo_001.png
    :class: sphx-glr-single-img




Plot each markevery case for log x and y scales



.. code-block:: python


    fig2, axs = plt.subplots(rows, cols, figsize=figsize, constrained_layout=True)
    axs = trim_axs(axs, len(cases))
    for ax, case in zip(axs, cases):
        ax.set_title('markevery=%s' % str(case))
        ax.set_xscale('log')
        ax.set_yscale('log')
        ax.plot(x, y, 'o', ls='-', ms=4, markevery=case)




.. image:: /gallery/lines_bars_and_markers/images/sphx_glr_markevery_demo_002.png
    :class: sphx-glr-single-img




Plot each markevery case for linear x and y scales but zoomed in
note the behaviour when zoomed in.  When a start marker offset is specified
it is always interpreted with respect to the first data point which might be
different to the first visible data point.



.. code-block:: python


    fig3, axs = plt.subplots(rows, cols, figsize=figsize, constrained_layout=True)
    axs = trim_axs(axs, len(cases))
    for ax, case in zip(axs, cases):
        ax.set_title('markevery=%s' % str(case))
        ax.plot(x, y, 'o', ls='-', ms=4, markevery=case)
        ax.set_xlim((6, 6.7))
        ax.set_ylim((1.1, 1.7))

    # define data for polar plots
    r = np.linspace(0, 3.0, 200)
    theta = 2 * np.pi * r




.. image:: /gallery/lines_bars_and_markers/images/sphx_glr_markevery_demo_003.png
    :class: sphx-glr-single-img




Plot each markevery case for polar plots



.. code-block:: python


    fig4, axs = plt.subplots(rows, cols, figsize=figsize,
            subplot_kw={'projection': 'polar'}, constrained_layout=True)
    axs = trim_axs(axs, len(cases))
    for ax, case in zip(axs, cases):
        ax.set_title('markevery=%s' % str(case))
        ax.plot(theta, r, 'o', ls='-', ms=4, markevery=case)

    plt.show()



.. image:: /gallery/lines_bars_and_markers/images/sphx_glr_markevery_demo_004.png
    :class: sphx-glr-single-img





.. _sphx_glr_download_gallery_lines_bars_and_markers_markevery_demo.py:


.. only :: html

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



  .. container:: sphx-glr-download

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



  .. container:: sphx-glr-download

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