Table of Contents

matplotlib

 Notes by Dan Peirce (reformated from my pages at 
           danpeirce.net46.net/dokuwiki/

Introduction

This Python language extension was created to combine plotting capabilities similar to Matlab (similar syntax) with the Python programming language. There is a introduction to matplotlib at http://matplotlib.sourceforge.net/users/intro.html . matplotlib requires another language extension called NumPy which processes large arrays efficiently. NumPy is pre-installed on the Raspberry Pi Rasbian image.

From that link one can also find a tutorial on how to make plots from data. As a simple python example that generated the plot shown down below:

import numpy as np
import matplotlib.pyplot as plt

# evenly sampled time at 200ms intervals
t = np.arange(0., 5., 0.2)

# red dashes, blue squares and green triangles
plt.plot(t, t, 'r--', t, t**2, 'bs', t, t**3, 'g^')
plt.show()

This little Python script generated this plot (was run on the Raspberry Pi )

The image shown above was saved as a *.png file. A screen shot of how it looks on the Raspberry Pi remote desktop is shown below. This is the screenshot with the remote Raspberry Pi desktop sitting on a windows XP desktop using the tightvnc viewer. This can also be viewed on an Android tablet using android- vnc-viewer

Installation

The Raspbian image has Python already installed. numpy is also installed. To get matplotlib running on also needs python-matplotlib . To install just run the following:

sudo apt-get install python-matplotlib

You may also want to install the documentation

sudo apt-get install python-matplotlib-doc

After the documentation install the manual will be available at

These packages can also be installed on windows PC's.

Advantages over Using Tkinter for Plotting

Matplotlab is a library that allows one to create a graphical plot without worrying about the details of creating a GUI since matplotlab creates the graphical window transparently in the background. It also creates good quality plots with scales on the axis. For an alternative using Tkinter see

Python has an interactive shell. IPython was developed to provide a more feature rich interactive shell (by a physicist). Can install debian package python-ipython and python-ipython-doc.