樱花数据集的Logistic回归

 绘制散点图

import matplotlib.pyplot as plt
import numpy as np
from sklearn.datasets import load_iris
iris = load_iris()
#获取花卉两列数据集
DD = iris.data
X = [x[0] for x in DD]
Y = [x[1] for x in DD]
plt.scatter(X[:50], Y[:50], color='red', marker='o', label='setosa')
plt.scatter(X[50:100], Y[50:100], color='blue', marker='x', label='versicolor')
plt.scatter(X[100:], Y[100:],color='green', marker='+', label='Virginica')
plt.legend(loc=2) #左上角
plt.show()

运行结果

逻辑回归分析

from sklearn.linear_model import LogisticRegression
iris = load_iris()
X = iris.data[:, :2]   #获取花卉两列数据集
Y = iris.target
lr = LogisticRegression(C=1e5)
lr.fit(X,Y)
#meshgrid函数生成两个网格矩阵
h = .02
x_min, x_max = X[:, 0].min()-.5, X[:, 0].max()+.5
y_min, y_max = X[:, 1].min()-.5, X[:, 1].max()+.5
xx, yy = np.meshgrid(np.arange(x_min, x_max, h), np.arange(y_min, y_max, h))
Z = lr.predict(np.c_[xx.ravel(), yy.ravel()])
Z = Z.reshape(xx.shape)
plt.figure(1, figsize=(8,6))
plt.pcolormesh(xx, yy, Z, cmap=plt.cm.Paired) #　按ｚ的不同，颜色不一样
plt.scatter(X[:50,0], X[:50,1], color='red',marker='o', label='setosa')
plt.scatter(X[50:100,0], X[50:100,1], color='blue', marker='x', label='versicolor')
plt.scatter(X[100:,0], X[100:,1], color='green', marker='s', label='Virginica')
plt.xlabel('Sepal length')
plt.ylabel('Sepal width')
plt.xlim(xx.min(), xx.max())
plt.ylim(yy.min(), yy.max())
plt.xticks(())
plt.yticks(())
plt.legend(loc=2)
plt.show()

运行结果