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
MS UC 2013-0-Prepare Tool
查看>>
msbuild发布web应用程序
查看>>
MSCRM调用外部JS文件
查看>>
MSEdgeDriver (Chromium) 不适用于版本 >= 79.0.313 (Canary)
查看>>
msf
查看>>
MSSQL数据库查询优化(一)
查看>>
MSSQL日期格式转换函数(使用CONVERT)
查看>>
MSTP多生成树协议(第二课)
查看>>
MSTP是什么?有哪些专有名词?
查看>>
Mstsc 远程桌面链接 And 网络映射
查看>>
Myeclipse常用快捷键
查看>>
MyEclipse用(JDBC)连接SQL出现的问题~
查看>>
myeclipse的新建severlet不见解决方法
查看>>
MyEclipse设置当前行背景颜色、选中单词前景色、背景色
查看>>
MyEclipse配置SVN
查看>>
MTCNN 人脸检测
查看>>
MyEcplise中SpringBoot怎样定制启动banner?
查看>>
MyPython
查看>>
MTD技术介绍
查看>>
MySQL
查看>>