关于R中的K折叠交叉验证
我创建这个函数代码是为了对逻辑回归执行5次交叉验证关于R中的K折叠交叉验证,r,cross-validation,confusion-matrix,R,Cross Validation,Confusion Matrix,我创建这个函数代码是为了对逻辑回归执行5次交叉验证 require(ISLR) folds <- cut(seq(1,nrow(Smarket)),breaks=5,labels=FALSE) log_cv=sapply(1:5,function(x) { set.seed(123) testIndexes <- which(folds==x,arr.ind=TRUE) testData &
require(ISLR)
folds <- cut(seq(1,nrow(Smarket)),breaks=5,labels=FALSE)
log_cv=sapply(1:5,function(x)
{
set.seed(123)
testIndexes <- which(folds==x,arr.ind=TRUE)
testData <- Smarket[testIndexes, ]
trainData <- Smarket[-testIndexes, ]
glm_log=glm(Direction ~ Lag1 + Lag2 + Lag3 +
Lag4 + Lag5 + Volume ,family = "binomial", data = trainData)
glm.prob <- predict(glm_log, testData, "response")
glm.pred <- ifelse(glm.prob >= 0.5, 1, 0)
return(glm.pred)
}
)
有没有办法结合上述结果,使用5倍交叉验证得到混淆矩阵?混淆矩阵由真阳性、假阳性、真阴性、假阴性的数量组成。通过交叉验证,您需要每个折叠的平均值。您有一个预测矩阵,
log\u cv
,需要与您的testData
进行比较
一种方法是将测试数据转换为矩阵,尽管我相信这里的其他人会推荐tidyverse:
truth <- matrix(testData$response, ncol = 5, nrow = nrow(testData))
真正的否定:
mean(apply(!truth & !testData, 2, sum))
mean(apply(!truth & testData, 2, sum))
误报:
mean(apply(truth & testData, 2, sum))
mean(apply(truth & !testData, 2, sum))
假阴性:
mean(apply(!truth & !testData, 2, sum))
mean(apply(!truth & testData, 2, sum))