How To Use Matplotlib In Python And Ipython To Draw Single Line Plot Example

This article will show you how to use matplotlib to draw single line plot graph in python and ipython.

1. Check Matplotlib Has Been Installed Correctlly.

Before coding, we should confirm that matplotlib has been installed correctly.

1. Open a terminal and run pip show matplotlibcommand, if you find below output message, then it means the matplotlib python package has been installed successfully.

   $ pip show matplotlib
   Name: matplotlib
   Version: 3.0.2
   Summary: Python plotting package
   Home-page: http://matplotlib.org
   Author: John D. Hunter, Michael Droettboom
   Author-email: [email protected]
   License: BSD
   Location: /home/zhaosong/anaconda3/lib/python3.7/site-packages
   Requires: numpy, cycler, kiwisolver, pyparsing, python-dateutil
   Required-by: seaborn, scikit-image
   

2. If you find matplotlib has not been installed, you can read article How To Install Anaconda On Linux, Windows, MacOS Correctly to install anaconda in your operation system, because anaconda has installed all matplotlib dependent libraries, so after you install anaconda, matplotlib should be installed also.

2. Use Matplotlib To Draw Single Line Chart In Python Command.

1. Open terminal and run python command to go to python interactive console.

   $ python
   Python 3.7.1 (default, Dec 14 2018, 19:28:38) 
   [GCC 7.3.0] :: Anaconda, Inc. on linux
   Type "help", "copyright", "credits" or "license" for more information.
   

2. Import matplotlib.pyplot module, and alias the module with name plt.

   >>> import matplotlib.pyplot as plt
   

3. Draw a single line chart use pyplot.plot function. Please note the plot function first parameter is a number list which represent vertical axis ( y – axis ).

   >>> plt.plot([1,3,8,16])
   [<matplotlib.lines.Line2D object at 0x7fb381109748>]
   

4. Display the chart image with plt.show() command.

   >>> plt.show()

5. Then you will see a dialog popup with the one line chart displayed. You can see there are four point has been connected with straight line.
   
6. If you want to save above picture to a local png file, you can run below method to replace plt.show(). Then you can exist python interactive environment and find the test.png file in current directory.

   >>> plt.savefig('test.png')
   
   >>> exit()
   
   $ ls -l

3. Use Matplotlib To Draw Single Line Plot In iPython.

1. Startup jupyter notebook web server by execute command $ jupyter notebook in a terminal.
2. If above command show any errors, please read article How To Use IPython Jupyter Notebook To Develop Python Code.
3. Then a web browser will open and direct you to the jupyter notebook web gui page.
4. Create a new .ipynb file by click New —> Python 3 menu item.
   
5. Input below python code in the first line cell, and click the Run button, then you will see the generated image test1.png below it.

   import matplotlib.pyplot as plt
   plt.plot([1,3,8,16])
   
   plt.savefig('test1.png')