Matplotlib scatterplot legend

Question

This is a repeat of a common question, but I've spent 4 hours reading responses and I still can't make sense of them and my code throws errors or returns unexpected results.

This task is so simple that it should be no more than a single line of code. Responses are either walls of code or they execute the scatter plot by doing a separate plt.scatter call for each class, which I don't want to do.

How do I make a legend for this? X and y data was fabricated with make_blobs.

map = {0: 'red', 1:'green', 2:"blue"}
plt.scatter(X[:,0], X[:,1], c=[map[i] for i in y])

All I want is a legend that looks like:
(red dot): 0
(green dot): 1
(blue dot): 2

ffs

The simple thing is to loop through your classes. But since you don t want to do that, you will have to figure out walls of code. — Jody Klymak, Jun 21 '22 at 05:59
Does this answer your question? [Matplotlib scatter plot with legend](https://stackoverflow.com/questions/26558816/matplotlib-scatter-plot-with-legend) — Jody Klymak, Jun 21 '22 at 06:01

score 2 · Accepted Answer · answered Jun 21 '22 at 02:41

as the full code is not available, I am just creating dummy data with 4 entries to demonstrate how to create scatter plot with the 3 colors you are talking about. This will create the legend based on what you enter in map.

import matplotlib.pyplot as plt 
data = {'x1': [1, 3, 6, 9], #Your X values
        'x2':[15, 11, 5, 8], #Your Y values 
        'y': [0,1,2,1]}  #The colors you want for each circle
X=pd.DataFrame(data)

map = {0: 'red', 1:'green', 2:"blue"}
fig, ax = plt.subplots()
for g in X.y.unique():  #For each group R/G/B
    ix = np.where(X.y == g)
    ax.scatter(X.x1[ix[0]], X.x2[ix[0]], c = map[g], label = map[g], s = 50) #Draw with said color
ax.legend()
plt.show()

Output graph

Matplotlib scatterplot legend

1 Answers1