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
MySQL8找不到my.ini配置文件以及报sql_mode=only_full_group_by解决方案
查看>>
mysql8的安装与卸载
查看>>
MySQL8,体验不一样的安装方式!
查看>>
MySQL: Host '127.0.0.1' is not allowed to connect to this MySQL server
查看>>
Mysql: 对换(替换)两条记录的同一个字段值
查看>>
mysql:Can‘t connect to local MySQL server through socket ‘/var/run/mysqld/mysqld.sock‘解决方法
查看>>
MYSQL:基础——3N范式的表结构设计
查看>>
MYSQL:基础——触发器
查看>>
Mysql:连接报错“closing inbound before receiving peer‘s close_notify”
查看>>
mysqlbinlog报错unknown variable ‘default-character-set=utf8mb4‘
查看>>
mysqldump 参数--lock-tables浅析
查看>>
mysqldump 导出中文乱码
查看>>
mysqldump 导出数据库中每张表的前n条
查看>>
mysqldump: Got error: 1044: Access denied for user ‘xx’@’xx’ to database ‘xx’ when using LOCK TABLES
查看>>
Mysqldump参数大全(参数来源于mysql5.5.19源码)
查看>>
mysqldump备份时忽略某些表
查看>>
mysqldump实现数据备份及灾难恢复
查看>>
mysqldump数据库备份无法进行操作只能查询 --single-transaction
查看>>
mysqldump的一些用法
查看>>
mysqli
查看>>