How to add legend to matplotlib markup plot
I am trying to plot a PCA and one of the colors is label 1 and the other is label 2. When I want to add a legend with ax1.legend()
, I only get a label for the blue point, or no label at all. How do I add a legend with the correct labels for the blue and purple dots?
sns.set(style = 'darkgrid')
fig, ax1 = sns.plt.subplots()
x1, x2 = X_bar[:,0], X_bar[:,1]
ax1.scatter(x1, x2, 100, edgecolors='none', c = colors)
fig.set_figheight(8)
fig.set_figwidth(15)
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1 answer
It looks like you are painting every dot that oscillates between two colors. As per the answer to this question, sub-compute every nth entry in the numpy array. You can use numpys array slicing to build two separate arrays and then make legend as usual. For some sample data:
import numpy as np
import numpy.random as nprnd
import matplotlib.pyplot as plt
A = nprnd.randint(1000, size=100)
A.shape = (50,2)
x1, x2 = np.sort(A[:,0], axis=0), np.sort(A[:,1], axis=0)
x1
Out[50]:
array([ 46, 63, 84, 96, 118, 127, 137, 142, 181, 187, 187, 207, 210,
238, 238, 330, 334, 335, 346, 346, 350, 392, 400, 426, 467, 531,
550, 567, 569, 572, 583, 625, 637, 661, 671, 677, 698, 713, 777,
796, 837, 850, 866, 868, 874, 890, 919, 972, 992, 993])
x2
Out[51]:
array([ 2, 44, 49, 51, 72, 84, 86, 118, 120, 133, 150, 155, 156,
159, 199, 202, 250, 281, 289, 317, 317, 386, 405, 414, 427, 461,
507, 510, 543, 552, 553, 555, 559, 576, 618, 622, 633, 647, 665,
672, 682, 685, 745, 767, 776, 802, 808, 813, 847, 973])
labels=['blue','red']
fig, ax1 = plt.subplots()
ax1.scatter(x1[0::2], x2[0::2], 100, edgecolors='none', c='red', label = 'red')
ax1.scatter(x1[1::2], x2[1::2], 100, edgecolors='none', c='black', label = 'black')
plt.legend()
plt.show()
For your code, you can:
sns.set(style = 'darkgrid')
fig, ax1 = sns.plt.subplots()
x1, x2 = X_bar[:,0], X_bar[:,1]
ax1.scatter(x1[0::2], x2[0::2], 100, edgecolors='none', c = colors[0], label='one')
ax1.scatter(x1[1::2], x2[1::2], 100, edgecolors='none', c = colors[1], label='two')
fig.set_figheight(8)
fig.set_figwidth(15)
plt.legend()
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