Legend is a method present in the Matplotlib package which represents the area to describe the elements in a plot/graph.
The order of labels in the legend region was based on the order we add the lines(data) to the plot.
Example:
Let us consider a DataFrame that stores student marks in weekly tests.
|
|
Raju |
Hari |
Bablu |
Dora |
|---|---|---|---|---|
|
Test-1 |
8 |
6 |
9 |
10 |
|
Test-2 |
10 |
4 |
9 |
9 |
|
Test-3 |
7 |
6 |
9 |
10 |
|
Test-4 |
7 |
7 |
9 |
9 |
|
Test-5 |
10 |
6 |
9 |
10 |
The above table stores the 4 student marks in 5 tests. Now plot the graph with legend using the above data.
Python3
# import necessary packages import pandas as pd import matplotlib.pyplot as plt # create a dataframe Marks = pd.DataFrame({'Raju': [8, 10, 7, 7, 10], 'Hari': [6, 4, 6, 7, 6], 'Bablu': [9, 9, 9, 9, 9], 'Dora': [10, 9, 10, 9, 10]}) # plot marks of each student plt.plot(Marks['Raju'], label="Raju Marks", color="Red") plt.plot(Marks['Hari'], label="Hari Marks", color="Blue") plt.plot(Marks['Bablu'], label="Bablu Marks", color="Yellow") plt.plot(Marks['Dora'], label="Dora Marks", color="Black") # labelling the axes plt.xlabel("Tests") plt.ylabel("Marks") # add legend to plot plt.legend() plt.show() |
Output
Change order of items in the legend
The above order of elements in the legend region can be changed by the gca method that uses another sub-method called get_legend_handles_labels method.
Syntax
handles, labels = plt.gca().get_legend_handles_labels()
These handles and labels lists are passed as parameters to legend method with order of indexes.
Consider the below example code for detailed understanding.
Example 1:
In this code, we used the same DataFrame we used in the above code. But used the above-specified methods to change the order of elements in the legend region.
Python3
# import necessary packages import pandas as pd import matplotlib.pyplot as plt # create a dataframe Marks = pd.DataFrame({'Raju': [8, 10, 7, 7, 10], 'Hari': [6, 4, 6, 7, 6], 'Bablu': [9, 9, 9, 9, 9], 'Dora': [10, 9, 10, 9, 10]}) # plot marks of each student plt.plot(Marks['Raju'], label="Raju Marks", color="Red") plt.plot(Marks['Hari'], label="Hari Marks", color="Blue") plt.plot(Marks['Bablu'], label="Bablu Marks", color="Yellow") plt.plot(Marks['Dora'], label="Dora Marks", color="Black") # labelling the axes plt.xlabel("Tests") plt.ylabel("Marks") # reordering the labels handles, labels = plt.gca().get_legend_handles_labels() # specify order order = [2, 3, 1, 0] # pass handle & labels lists along with order as below plt.legend([handles[i] for i in order], [labels[i] for i in order]) plt.show() |
Output
Example 2:
Below is the implementation of plotting a graph that represents student marks along with legend with specified order in legend region.
Python3
# import necessary packages import pandas as pd import matplotlib.pyplot as plt # create a dataframe Marks = pd.DataFrame({'Raju': [8, 10, 7, 7, 10], 'Hari': [6, 4, 6, 7, 6], 'Bablu': [9, 9, 9, 9, 9], 'Dora': [10, 9, 10, 9, 10]}) # plot marks of each student plt.plot(Marks['Raju'], label="Raju Marks", color="Red") plt.plot(Marks['Hari'], label="Hari Marks", color="Blue") plt.plot(Marks['Bablu'], label="Bablu Marks", color="Yellow") plt.plot(Marks['Dora'], label="Dora Marks", color="Black") # labelling the axes plt.xlabel("Tests") plt.ylabel("Marks") # reordering the labels handles, labels = plt.gca().get_legend_handles_labels() # specify order order = [3, 2, 1, 0] # pass handle & labels lists along with order as below plt.legend([handles[i] for i in order], [labels[i] for i in order]) plt.show() |
Output
