Matplotlib Tutorial
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Matplotlib - Formatting Axes



Axes object is the region of the image with the data space. It mainly contains two or three-axis(in case of 3D) objects which then take care of the data limits. Below is an image illustrating the different parts of a figure which contains the graph.

Formatting-axes

Let see how can we change different aspects of the Axes according to the requirements.

Axes Title & Labels

For setting title, the Axes.set_title() function is used. For setting x-axis and y-axis labels, Axes.set_xlabel() and Axes.set_ylabel() functions are used respectively.

Syntax

#sets a title for the Axes
Axes.set_title(self, loc='center')	

#sets the label for the x-axis
Axes.set_xlabel(self, xlabel, labelpad=None, 
                loc=None, **kwargs)

#sets the label for the y-axis
Axes.set_ylabel(self, ylabel, labelpad=None, 
                loc=None, **kwargs)	

Parameters

xlabel, ylabel Required. Specify label text.
labelpad Optional. Specify float. Spacing in points from the axes bounding box including ticks and tick labels. Default: 4.0
loc Optional. Specify the label position. It can take value from {'left', 'center', 'right'}.

Example:

In the example below, the axes labels and title are set.

import matplotlib.pyplot as plt
import numpy as np

#creating a array of values between
#0 to 10 with a difference of 0.1
x = np.arange(0, 10, 0.1)
y = np.sin(x)

fig, ax = plt.subplots()

#plotting curves
ax.plot(x, y) 

#formatting axes
ax.set_title("Sine Wave") 
ax.set_xlabel("x")
ax.set_ylabel("y = sin(x)")

#displaying the figure
plt.show()

The output of the above code will be:

Formatting-axes

Axes Legend

For setting legend, the Axes.legend() function is used.

Syntax

#sets a title for the Axes
Axes.legend(self, *args, **kwargs)

The call signatures are:

#Automatic detection of elements for legend
legend()

#Labeling existing plot elements
legend(labels)

#Explicitly defining the elements for legend
legend(handles, labels)

Along with this, the location of the legend can be specified using loc parameter. It can take value from below table:

Location StringLocation Code
'best'0
'upper right'1
'upper left'2
'lower left'3
'lower right'4
'right'5
'center left'6
'center right'7
'lower center'8
'upper center'9
'center'10

Example:

In the example below, the axes legend is set using legend(labels) calling signature.

import matplotlib.pyplot as plt
import numpy as np

#creating a array of values between
#0 to 10 with a difference of 0.1
x = np.arange(0, 10, 0.1)
y1 = np.sin(x)
y2 = np.cos(x)

fig, ax = plt.subplots()

#plotting curves
ax.plot(x, y1) 
ax.plot(x, y2) 

#formatting axes
ax.set_xlabel("x")
ax.set_ylabel("y")
ax.set_title("Sine vs Cosine") 

#adding legend
ax.legend(['sin(x)', 'cos(x)'], loc=0) 

#displaying the figure
plt.show()

The output of the above code will be:

Formatting-axes

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