第五节 matplotlib

1matplotlib基础

1.1折线图

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

x = np.linspace(0, 10, 100)
y = np.sin(x)
z= np.cos(x)

plt.plot(x, y, label='正弦')
plt.plot(x, z, color='red', linestyle='--', label='余弦')
plt.xlim(-5, 10)
plt.ylim(0, 1.5)
# 用axis直接设置x和y的范围
plt.axis([-1, 10, -2, 2])
plt.xlable('x axis')
plt.ylabel('y value')
plt.legend()
plt.title('正弦余弦曲线')
plt.show()

1.2散点图

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

x = np.linspace(0, 10, 100)
y = np.sin(x)
z= np.cos(x)

plt.scatter(x, y, label='正弦', alpha=0.2)
plt.scatter(x, z, color='red', linestyle='--', label='余弦', alpha=0.3)
plt.xlim(-5, 10)
plt.ylim(0, 1.5)
# 用axis直接设置x和y的范围
plt.axis([-1, 10, -2, 2])
plt.xlable('x axis')
plt.ylabel('y value')
plt.legend()
plt.title('正弦余弦曲线')
plt.show()

2读取数据和简单的数据搜索

import matplotlib as mpl
import numpy as np
import matplotlib.pyplot as plt
from sklearn import datasets

# 加载自带的鸢尾花数据集
iris = datasets.load_iris()
iris.keys()
# x是特征数据
x = iris.data[:, :2]
# y是特征结果，分好类的结果
y = iris.target
# 画出所有散点，对花类别不作区分
plt.scatter(x[:, 0], x[: ,1] )

plt.scatter(x[y==0, 0], x[y==0,1], color='red', marker='o')
plt.scatter(x[y==1, 0], x[y==1,1], color='blue', marker='+')
plt.scatter(x[y==2, 0], x[y==2,1], color='green', marker='x')
plt.show()