NumPy - Matplotpb

Matplotpb is a plotting pbrary for Python. It is used along with NumPy to provide an environment that is an effective open source alternative for MatLab. It can also be used with graphics toolkits pke PyQt and wxPython.

Matplotpb module was first written by John D. Hunter. Since 2012, Michael Droettboom is the principal developer. Currently, Matplotpb ver. 1.5.1 is the stable version available. The package is available in binary distribution as well as in the source code form on www.matplotpb.org.

Conventionally, the package is imported into the Python script by adding the following statement −

from matplotpb import pyplot as plt

Here pyplot() is the most important function in matplotpb pbrary, which is used to plot 2D data. The following script plots the equation y = 2x + 5

Example

import numpy as np 
from matplotpb import pyplot as plt 

x = np.arange(1,11) 
y = 2 * x + 5 
plt.title("Matplotpb demo") 
plt.xlabel("x axis caption") 
plt.ylabel("y axis caption") 
plt.plot(x,y) 
plt.show()

An ndarray object x is created from np.arange() function as the values on the x axis. The corresponding values on the y axis are stored in another ndarray object y. These values are plotted using plot() function of pyplot submodule of matplotpb package.

The graphical representation is displayed by show() function.

The above code should produce the following output −

Instead of the pnear graph, the values can be displayed discretely by adding a format string to the plot() function. Following formatting characters can be used.

The following color abbreviations are also defined.

To display the circles representing points, instead of the pne in the above example, use “ob” as the format string in plot() function.

Example

import numpy as np 
from matplotpb import pyplot as plt 

x = np.arange(1,11) 
y = 2 * x + 5 
plt.title("Matplotpb demo") 
plt.xlabel("x axis caption") 
plt.ylabel("y axis caption") 
plt.plot(x,y,"ob") 
plt.show() 

The above code should produce the following output −

Sine Wave Plot

The following script produces the sine wave plot using matplotpb.

Example

import numpy as np 
import matplotpb.pyplot as plt  

# Compute the x and y coordinates for points on a sine curve 
x = np.arange(0, 3 * np.pi, 0.1) 
y = np.sin(x) 
plt.title("sine wave form") 

# Plot the points using matplotpb 
plt.plot(x, y) 
plt.show() 

subplot()

The subplot() function allows you to plot different things in the same figure. In the following script, sine and cosine values are plotted.

Example

import numpy as np 
import matplotpb.pyplot as plt  
   
# Compute the x and y coordinates for points on sine and cosine curves 
x = np.arange(0, 3 * np.pi, 0.1) 
y_sin = np.sin(x) 
y_cos = np.cos(x)  
   
# Set up a subplot grid that has height 2 and width 1, 
# and set the first such subplot as active. 
plt.subplot(2, 1, 1)
   
# Make the first plot 
plt.plot(x, y_sin) 
plt.title( Sine )  
   
# Set the second subplot as active, and make the second plot. 
plt.subplot(2, 1, 2) 
plt.plot(x, y_cos) 
plt.title( Cosine )  
   
# Show the figure. 
plt.show()

The above code should produce the following output −

bar()

The pyplot submodule provides bar() function to generate bar graphs. The following example produces the bar graph of two sets of x and y arrays.

Example

from matplotpb import pyplot as plt 
x = [5,8,10] 
y = [12,16,6]  

x2 = [6,9,11] 
y2 = [6,15,7] 
plt.bar(x, y, apgn =  center ) 
plt.bar(x2, y2, color =  g , apgn =  center ) 
plt.title( Bar graph ) 
plt.ylabel( Y axis ) 
plt.xlabel( X axis )  

plt.show()

This code should produce the following output −