[分类算法]常用功能实现

前言：分类是机器学习中的重要的一种功能，在机器学习的研究历史中，诞生了大量的分类算法，而每种算法都有其优势和不足。

本文汇总了常用的分类算法及其实现方式，方便快速查询使用。（本文使用鸢尾花数据集，是三类别分类）

以下9种分类算法，使用相同的数据进行训练和测试，在测试集上的准确率(accuracy)分别为：

1.随机森林：100%

2.决策树：100%

3.K近邻：100%

4.支持向量机：100%

5.逻辑回归：96.67%

6.线性支持向量机：100%

1 import numpy as np
  2 import pandas as pd
  3 import matplotlib as mpl
  4 import matplotlib.pyplot as plt
  5 import sklearn
  6 from sklearn import datasets
  7 from sklearn.metrics import accuracy_score
  8 
  9 from sklearn.ensemble import RandomForestClassifier
 10 from sklearn.tree import DecisionTreeClassifier
 11 
 12 from sklearn.neighbors import KNeighborsClassifier
 13 from sklearn.svm import SVC, LinearSVC
 14 from sklearn.linear_model import LogisticRegression
 15 
 16 from sklearn.linear_model import SGDClassifier
 17 from sklearn.linear_model import Perceptron
 18 from sklearn.naive_bayes import GaussianNB
 19 
 20 from sklearn.model_selection import train_test_split
 21 from sklearn.model_selection import cross_val_score
 22 
 23 from sklearn.model_selection import GridSearchCV
 24 
 25 iris = datasets.load_iris()
 26 x,y = iris.data,iris.target
 27 
 28 x_train,x_test,y_train,y_test = train_test_split(x,y,test_size=0.2,random_state=0)
 29 
 30 res = []
 31 
 32 #1. 随机森林分类
 33 print('随机森林分类')
 34 clf = RandomForestClassifier(n_estimators=100)
 35 clf.fit(x_train, y_train)
 36 cross_score = cross_val_score(clf, x_train, y_train, cv=3, scoring="accuracy")
 37 print(cross_score)
 38 y_predict = clf.predict(x_test)
 39 score = accuracy_score(y_test,y_predict)
 40 res.append(score)
 41 print()
 42 
 43 #2. 决策树分类
 44 print('决策树分类')
 45 clf = DecisionTreeClassifier()
 46 clf.fit(x_train, y_train)
 47 cross_score = cross_val_score(clf, x_train, y_train, cv=3, scoring="accuracy")
 48 print(cross_score)
 49 y_predict = clf.predict(x_test)
 50 score = accuracy_score(y_test,y_predict)
 51 res.append(score)
 52 print()
 53 
 54 #3. KNN
 55 print('KNN')
 56 clf = KNeighborsClassifier(n_neighbors = 13)
 57 clf.fit(x_train, y_train)
 58 cross_score = cross_val_score(clf, x_train, y_train, cv=3, scoring="accuracy")
 59 print(cross_score)
 60 y_predict = clf.predict(x_test)
 61 score = accuracy_score(y_test,y_predict)
 62 res.append(score)
 63 print()
 64 
 65 #4. SVM分类
 66 print('SVM')
 67 clf = SVC(gamma='scale')
 68 clf.fit(x_train, y_train)
 69 cross_score = cross_val_score(clf, x_train, y_train, cv=3, scoring="accuracy")
 70 print(cross_score)
 71 y_predict = clf.predict(x_test)
 72 score = accuracy_score(y_test,y_predict)
 73 res.append(score)
 74 print()
 75 
 76 #5. 逻辑回归分类
 77 print('LogisticRegression')
 78 clf = LogisticRegression(solver='lbfgs',multi_class='ovr')
 79 clf.fit(x_train, y_train)
 80 cross_score = cross_val_score(clf, x_train, y_train, cv=3, scoring="accuracy")
 81 print(cross_score)
 82 y_predict = clf.predict(x_test)
 83 score = accuracy_score(y_test,y_predict)
 84 res.append(score)
 85 print()
 86 
 87 #6. linear svm分类
 88 print('linear SVM')
 89 clf = LinearSVC(max_iter=10000)
 90 clf.fit(x_train, y_train)
 91 cross_score = cross_val_score(clf, x_train, y_train, cv=3, scoring="accuracy")
 92 print(cross_score)
 93 y_predict = clf.predict(x_test)
 94 score = accuracy_score(y_test,y_predict)
 95 res.append(score)
 96 print()
 97 
 98 #7. 随机梯度下降分类
 99 print('SGD')
100 clf = SGDClassifier(max_iter=1000,tol=1e-3)
101 clf.fit(x_train, y_train)
102 cross_score = cross_val_score(clf, x_train, y_train, cv=3, scoring="accuracy")
103 print(cross_score)
104 y_predict = clf.predict(x_test)
105 score = accuracy_score(y_test,y_predict)
106 res.append(score)
107 print()
108 
109 #8. 感知机分类
110 print('Perceptron')
111 clf = Perceptron(max_iter=1000,tol=1e-3)
112 clf.fit(x_train, y_train)
113 cross_score = cross_val_score(clf, x_train, y_train, cv=3, scoring="accuracy")
114 print(cross_score)
115 y_predict = clf.predict(x_test)
116 score = accuracy_score(y_test,y_predict)
117 res.append(score)
118 print()
119 
120 #9. 朴素贝叶斯分类
121 print('Naive Bayes')
122 clf = GaussianNB()
123 clf.fit(x_train, y_train)
124 cross_score = cross_val_score(clf, x_train, y_train, cv=3, scoring="accuracy")
125 print(cross_score)
126 y_predict = clf.predict(x_test)
127 score = accuracy_score(y_test,y_predict)
128 res.append(score)
129 print()
130 
131 #10. 得分比较
132 print(res)