博客
关于我
逻辑回归_训练多元分类器
阅读量:378 次
发布时间:2019-03-05

本文共 1576 字,大约阅读时间需要 5 分钟。

逻辑回归_训练多元分类器

一对多

# 训练多元分类器from sklearn.linear_model import LogisticRegressionfrom sklearn import datasetsfrom sklearn.preprocessing import StandardScaler# 加载数据iris = datasets.load_iris()features = iris.datatarget = iris.target​scaler = StandardScaler()features_standardized = scaler.fit_transform(features)# multi_class="ovr"   表示一对多的逻辑回归    另外一种是MLR 多元逻辑回归logistic_regression = LogisticRegression(random_state=0, multi_class="ovr")#logistic_regression_MNL = LogisticRegression(random_state=0, multi_class="multinomial")# 训练模型model = logistic_regression.fit(features_standardized, target)DiscussionOn their own, logistic regressions are only binary classifiers, meaning they cannot handle target vectors with more than two classes. However, two clever extensions to logistic regression do just that. First, in one-vs-rest logistic regression (OVR) a separate model is trained for each class predicted whether an observation is that class or not (thus making it a binary classification problem). It assumes that each observation problem (e.g. class 0 or not) is independentAlternatively in multinomial logistic regression (MLR) the logistic function we saw in Recipe 15.1 is replaced with a softmax function:P(yI=k|X)=eβkxi∑Kj=1eβjxiP(yI=k|X)=eβkxi∑j=1Keβjxi where  P(yi=k|X)P(yi=k|X)  is the probability of the ith observation's target value,  yiyi , is class k, and K is the total number of classes. One practical advantage of the MLR is that its predicted probabilities using predict_proba method are more reliableWe can switch to an MNL by setting multi_class='multinomial'

转载地址:http://xprg.baihongyu.com/

你可能感兴趣的文章
mysql 多字段删除重复数据,保留最小id数据
查看>>
MySQL 多表联合查询:UNION 和 JOIN 分析
查看>>
MySQL 大数据量快速插入方法和语句优化
查看>>
mysql 如何给SQL添加索引
查看>>
mysql 字段区分大小写
查看>>
mysql 字段合并问题(group_concat)
查看>>
mysql 字段类型类型
查看>>
MySQL 字符串截取函数,字段截取,字符串截取
查看>>
MySQL 存储引擎
查看>>
mysql 存储过程 注入_mysql 视图 事务 存储过程 SQL注入
查看>>
MySQL 存储过程参数:in、out、inout
查看>>
mysql 存储过程每隔一段时间执行一次
查看>>
mysql 存在update不存在insert
查看>>
Mysql 学习总结(86)—— Mysql 的 JSON 数据类型正确使用姿势
查看>>
Mysql 学习总结(87)—— Mysql 执行计划(Explain)再总结
查看>>
Mysql 学习总结(88)—— Mysql 官方为什么不推荐用雪花 id 和 uuid 做 MySQL 主键
查看>>
Mysql 学习总结(89)—— Mysql 库表容量统计
查看>>
mysql 实现主从复制/主从同步
查看>>
mysql 审核_审核MySQL数据库上的登录
查看>>
mysql 导入 sql 文件时 ERROR 1046 (3D000) no database selected 错误的解决
查看>>