Adding legend to scatter plot in Python

Question

I have made a scatter plot in the following way:

f, ax1 = plt.subplots(3,2)
cmap = matplotlib.cm.get_cmap('coolwarm')
ax1[0,1].scatter(data[:,0], data[:,1], c=y, s=20, marker='o', alpha=.5, cmap=cmap)

data holds the data and y holds the labels (1,2,3). Now I would like to add a legend.

ax1[0,1].legend(('label1', 'label2', 'label3'),
           scatterpoints=1,
           loc='lower left',
           fontsize=10)

This does not work, it only prints label1. How can this be done otherwise?

Roman Fursenko · Accepted Answer · 2017-02-08 02:52:46Z

1

The idea is to divide data set on separate data sets which are represented by the same color. After that the legend displayed properly.

import matplotlib.pyplot as plt
import matplotlib
import numpy as np

data = np.zeros(shape=(10,2))
data[:,0] = np.linspace(0,1,10)
data[:,1] = np.linspace(0,1,10)

y = ['red', 'green', 'blue']
f, ax1 = plt.subplots(3,2)
cmap = matplotlib.cm.get_cmap('coolwarm')
ny = len(y)
for i, itm in enumerate(y):
    datac = data[i::ny,:]
    ax1[0,1].scatter(datac[:,0], datac[:,1], c=itm, 
                     s=20, marker='o', alpha=.5, cmap=cmap)

ax1[0,1].legend(['label1', 'label2', 'label3'],
           scatterpoints=1,
           loc='lower left',
           fontsize=10)
plt.show()

edited Feb 8, 2017 at 2:52

answered Feb 7, 2017 at 10:46

Roman Fursenko

6884 silver badges9 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Adding legend to scatter plot in Python

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related