.. only:: html
.. note::
:class: sphx-glr-download-link-note
Click :ref:`here ` 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 sphx-glr-download-python
:download:`Download Python source code: plotfile_demo_sgskip.py `
.. container:: sphx-glr-download sphx-glr-download-jupyter
:download:`Download Jupyter notebook: plotfile_demo_sgskip.ipynb `
.. only:: html
.. rst-class:: sphx-glr-signature
Keywords: matplotlib code example, codex, python plot, pyplot
`Gallery generated by Sphinx-Gallery
`_