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

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

.. _sphx_glr_gallery_misc_plotfile_demo_sgskip.py:


=========================
Plotting data from a file
=========================

Plotting data from a file is actually a two-step process.

1. Interpreting the file and loading the data.
2. Creating the actual plot.

`.pyplot.plotfile` tried to do both at once. But each of the steps has so many
possible variations and parameters that it does not make sense to squeeze both
into a single function. Therefore, `.pyplot.plotfile` has been deprecated.

The recommended way of plotting data from a file is therefore to use dedicated
functions such as `numpy.loadtxt` or `pandas.read_csv` to read the data. These
are more powerful and faster. Then plot the obtained data using matplotlib.

Note that `pandas.DataFrame.plot` is a convenient wrapper around Matplotlib
to create simple plots.


.. code-block:: default


    import matplotlib.pyplot as plt
    import matplotlib.cbook as cbook

    import numpy as np
    import pandas as pd


Using pandas
============

Subsequent are a few examples of how to replace `~.pyplot.plotfile` with
`pandas`. All examples need the the `pandas.read_csv` call first. Note that
you can use the filename directly as a parameter::

    msft = pd.read_csv('msft.csv')

The following slightly more involved `pandas.read_csv` call is only to make
automatic rendering of the example work:


.. code-block:: default


    fname = cbook.get_sample_data('msft.csv', asfileobj=False)
    with cbook.get_sample_data('msft.csv') as file:
        msft = pd.read_csv(file)


When working with dates, additionally call
`pandas.plotting.register_matplotlib_converters` and use the ``parse_dates``
argument of `pandas.read_csv`::


.. code-block:: default


    pd.plotting.register_matplotlib_converters()

    with cbook.get_sample_data('msft.csv') as file:
        msft = pd.read_csv(file, parse_dates=['Date'])



Use indices
-----------


.. code-block:: default


    # Deprecated:
    plt.plotfile(fname, (0, 5, 6))

    # Use instead:
    msft.plot(0, [5, 6], subplots=True)


Use names
---------


.. code-block:: default


    # Deprecated:
    plt.plotfile(fname, ('date', 'volume', 'adj_close'))

    # Use instead:
    msft.plot("Date", ["Volume", "Adj. Close*"], subplots=True)


Use semilogy for volume
-----------------------


.. code-block:: default


    # Deprecated:
    plt.plotfile(fname, ('date', 'volume', 'adj_close'),
                 plotfuncs={'volume': 'semilogy'})

    # Use instead:
    fig, axs = plt.subplots(2, sharex=True)
    msft.plot("Date", "Volume", ax=axs[0], logy=True)
    msft.plot("Date", "Adj. Close*", ax=axs[1])



Use semilogy for volume (by index)
----------------------------------


.. code-block:: default


    # Deprecated:
    plt.plotfile(fname, (0, 5, 6), plotfuncs={5: 'semilogy'})

    # Use instead:
    fig, axs = plt.subplots(2, sharex=True)
    msft.plot(0, 5, ax=axs[0], logy=True)
    msft.plot(0, 6, ax=axs[1])


Single subplot
--------------


.. code-block:: default


    # Deprecated:
    plt.plotfile(fname, ('date', 'open', 'high', 'low', 'close'), subplots=False)

    # Use instead:
    msft.plot("Date", ["Open", "High", "Low", "Close"])


Use bar for volume
------------------


.. code-block:: default


    # Deprecated:
    plt.plotfile(fname, (0, 5, 6), plotfuncs={5: "bar"})

    # Use instead:
    fig, axs = plt.subplots(2, sharex=True)
    axs[0].bar(msft.iloc[:, 0], msft.iloc[:, 5])
    axs[1].plot(msft.iloc[:, 0], msft.iloc[:, 6])
    fig.autofmt_xdate()


Using numpy
===========


.. code-block:: default


    fname2 = cbook.get_sample_data('data_x_x2_x3.csv', asfileobj=False)
    with cbook.get_sample_data('data_x_x2_x3.csv') as file:
        array = np.loadtxt(file)


Labeling, if no names in csv-file
---------------------------------


.. code-block:: default


    # Deprecated:
    plt.plotfile(fname2, cols=(0, 1, 2), delimiter=' ',
                 names=['$x$', '$f(x)=x^2$', '$f(x)=x^3$'])

    # Use instead:
    fig, axs = plt.subplots(2, sharex=True)
    axs[0].plot(array[:, 0], array[:, 1])
    axs[0].set(ylabel='$f(x)=x^2$')
    axs[1].plot(array[:, 0], array[:, 2])
    axs[1].set(xlabel='$x$', ylabel='$f(x)=x^3$')


More than one file per figure
-----------------------------


.. code-block:: default


    # For simplicity of the example we reuse the same file.
    # In general they will be different.
    fname3 = fname2

    # Depreacted:
    plt.plotfile(fname2, cols=(0, 1), delimiter=' ')
    plt.plotfile(fname3, cols=(0, 2), delimiter=' ',
                 newfig=False)  # use current figure
    plt.xlabel(r'$x$')
    plt.ylabel(r'$f(x) = x^2, x^3$')

    # Use instead:
    fig, ax = plt.subplots()
    ax.plot(array[:, 0], array[:, 1])
    ax.plot(array[:, 0], array[:, 2])
    ax.set(xlabel='$x$', ylabel='$f(x)=x^3$')

    plt.show()


.. _sphx_glr_download_gallery_misc_plotfile_demo_sgskip.py:


.. only :: html

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



  .. container:: sphx-glr-download

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



  .. container:: sphx-glr-download

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