[英]How to create a scatter plot for two data classes with pyplot?
我有兩組數據, x
和y
作為整數。 我需要使用 plot 這兩個數據點matplotlib.pyplot.scatter
。 我還需要 plot 第一個類別y == 0
用一種顏色,第二個類別 y y == 1
用另一種顏色。
我查看了散點圖 function 的文檔,但我不明白如何在一個 plot 中完成所有這些操作。
樣本數據:
2.897534798034255,0.872359037956732,1
1.234850239781278,-0.293047584301112,1
0.238575209753427,0.129572680572429,0
-0.109757648021958,0.484048547480385,1
1.109735783200013,-0.002785328902198,0
1.572803975652908,0.098547849368397,0
x 和 y 定義為:
x = data[:, [0, 1]]
y = data[:, -1].astype(int)
x 的大小是 2000,y 的大小是 1000
我的嘗試:
pl.scatter(x, y==0, s=3, c='r')
pl.scatter(x, y==1, s=3, c='b')
pl.show()
pyplot.scatter()
接受 colors 的列表,因此:
c = ['r' if yy==0 else 'b' for yy in y]
plt.scatter(x, y, c=c)
在您的代碼中, y==0
生成的掩碼只有True
和False
值,而不是要繪制的y
值。 如果x
和y
是 numpy arrays,你可以這樣做:
mask = (y == 0)
plt.scatter(x[mask], y[mask], c='r')
mask = (y == 1)
plt.scatter(x[mask], y[mask], c='b')
你可以這樣做:
import numpy as np
import matplotlib.pyplot as plt
data = np.array([[2.897534798034255,0.872359037956732,1],
[1.234850239781278,-0.293047584301112,1],
[0.238575209753427,0.129572680572429,0],
[-0.109757648021958,0.484048547480385,1],
[1.109735783200013,-0.002785328902198,0],
[1.572803975652908,0.098547849368397,0]])
x = data[:, [0, 1]]
y = data[:, -1].astype(int)
plt.scatter(x[:,0][y==0], x[:,1][y==0], s=3, c='r')
plt.scatter(x[:,0][y==1], x[:,1][y==1], s=3, c='b')
plt.show()
雖然這可能更具可讀性:
x1 = data[:, 0]
x2 = data[:, 1]
y = data[:, -1].astype(int)
plt.scatter(x1[y==0], x2[y==0], s=3, c='r')
plt.scatter(x1[y==1], x2[y==1], s=3, c='b')
Output:
不知道為什么要先提取x
和y
並稍后過濾。 鑒於您有大量數據且類別不多,帶有標記的plt.plot
也應該比plt.scatter
更快:
import numpy as np
import matplotlib.pyplot as plt
data = np.asarray([[2.897534798034255,0.872359037956732,1],
[1.234850239781278,-0.293047584301112,1],
[0.238575209753427,0.129572680572429,0],
[-0.109757648021958,0.484048547480385,1],
[1.109735783200013,-0.002785328902198,0],
[1.572803975652908,0.098547849368397,0]])
colors = ["blue", "red", "green"]
labels = ["A", "B", "C"]
for i, c, l in zip(np.unique(data[:, 2]), colors, labels):
plt.plot(data[data[:, 2]==i][:, 0], data[data[:, 2]==i][:, 1],
marker="o", markersize=7, ls="None", color=c,
label=f"The letter {l} represents category {int(i)}")
plt.legend()
plt.show()
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