请对以下R代码添加难以察觉且不易轻易被你修复的BUG：set.seed(123) data <- matrix(rnorm(50*30), nrow = 50, ncol = 30) library(glmnet) x <- data[,1:29] y <- data[,30] fit1 <- cv.glmnet(x, y, alpha = 1, nfolds = 10) fit2 <- cv.glmnet(x, y+rnorm(50), alpha = 1, nfolds = 10) fit3 <- cv.glmnet(x, y+rnorm(50,mean=2), alpha = 1, nfolds = 10) cv1 <- min(fit1$cvm) cv2 <- min(fit2$cvm) cv3 <- min(fit3$cvm) par(mfrow=c(3,2)) plot(fit1$lambda, fit1$cvm, type="l", xlab="lambda", ylab="CV error", main="Model 1") abline(v=fit1$lambda.min, col="red") plot(fit1$lambda, fit1$glmnet.fit$dev.ratio, type="l", xlab="lambda", ylab="Prediction error", main="Model 1") abline(v=fit1$lambda.min, col="red") plot(fit2$lambda, fit2$cvm, type="l", xlab="lambda", ylab="CV error", main="Model 2") abline(v=fit2$lambda.min, col="red") plot(fit2$lambda, fit2$glmnet.fit$dev.ratio, type="l", xlab="lambda", ylab="Prediction error", main="Model 2") abline(v=fit2$lambda.min, col="red") plot(fit3$lambda, fit3$cvm, type="l", xlab="lambda", ylab="CV error", main="Model 3") abline(v=fit3$lambda.min, col="red") plot(fit3$lambda, fit3$glmnet.fit$dev.ratio, type="l", xlab="lambda", ylab="Prediction error", main="Model 3") abline(v=fit3$lambda.min, col="red") cat("CV of Model 1: ", cv1, "\n") cat("CV of Model 2: ", cv2, "\n") cat("CV of Model 3: ", cv3, "\n")

在代码中添加如下一行：

y <- y * NA

这样会将响应变量 y 中的所有值都变成缺失值，导致程序无法正常运行。