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PyLab is a procedural interface to the Matplotlib object-oriented plotting library. Matplotlib is the whole package; matplotlib.pyplot is a module in Matplotlib; and PyLab is a module that gets installed alongside Matplotlib.
PyLab is a convenience module that bulk imports matplotlib.pyplot (for plotting) and NumPy (for Mathematics and working with arrays) in a single name space. Although many examples use PyLab, it is no longer recommended.
Basic Plotting
Plotting curves is done with the plot command. It takes a pair of same-length arrays (or sequences) −
from numpy import * from pylab import * x = linspace(-3, 3, 30) y = x**2 plot(x, y) show()
The above line of code generates the following output −
To plot symbols rather than lines, provide an additional string argument.
| symbols | – , –, -., , . , , , o , ^ , v , , s , + , x , D , d , 1 , 2 , 3 , 4 , h , H , p , | , _ |
| colors | b, g, r, c, m, y, k, w |
Now, consider executing the following code −
from pylab import * x = linspace(-3, 3, 30) y = x**2 plot(x, y, ''r.'') show()
It plots the red dots as shown below −
Plots can be overlaid. Just use the multiple plot commands. Use clf() to clear the plot.
from pylab import * plot(x, sin(x)) plot(x, cos(x), ''r-'') plot(x, -sin(x), ''g--'') show()
The above line of code generates the following output −
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