在运行以下R代码时：library(glmnet) library(ggplot2) # 生成5030的随机数据和30个变量 set.seed(1111) n <- 50 p <- 30 X <- matrix(runif(n * p), n, p) y <- rnorm(n) # 生成三组不同系数的线性模型 beta1 <- c(rep(1, 3), rep(0, p - 3)) beta2 <- c(rep(0, 10), rep(1, 3), rep(0, p - 13)) beta3 <- c(rep(0, 20), rep(1, 3), rep(0, p - 23)) y1 <- X %*% beta1 + rnorm(n) y2 <- X %*% beta2 + rnorm(n) y3 <- X %*% beta3 + rnorm(n) # 设置交叉验证折数 k <- 10 # 设置不同的lambda值 lambda_seq <- 10^seq(10, -2, length.out = 100) # 执行交叉验证和岭回归，并记录CV error和Prediction error cv_error <- list() pred_error <- list() for (i in 1:3) { # 交叉验证 cvfit <- cv.glmnet(X, switch(i, y1, y2, y3), alpha = 0, lambda = lambda_seq, nfolds = k) cv_error[[i]] <- cvfit$cvm # 岭回归 fit <- glmnet(X, switch(i, y1, y2, y3), alpha = 0, lambda = lambda_seq) pred_error[[i]] <- apply(X, 2, function(x) { x_mat <- matrix(x, nrow = n, ncol = p, byrow = TRUE) pred <- predict(fit, newx = x_mat) pred <- t(pred) # 转置 mean((x_mat %*% fit$beta - switch(i, y1, y2, y3))^2, na.rm = TRUE) # 修改此处 }) } # 绘制图形 par(mfrow = c(3, 2), mar = c(4, 4, 2, 1), oma = c(0, 0, 2, 0)) for (i in 1:3) { # CV error plot cv_plot_data <- cv_error[[i]] plot(log10(lambda_seq), cv_plot_data, type = "l", xlab = expression(log10), ylab = "CV error", main = paste0("Model ", i)) abline(v = log10(cvfit$lambda.min), col = "red") # Prediction error plot pred_plot_data <- pred_error[[i]] plot(log10(lambda_seq), pred_plot_data, type = "l", xlab = expression(log10), ylab = "Prediction error", main = paste0("Model ", i)) abline(v = log10(lambda_seq[which.min(pred_plot_data)]), col = "red") }。发生了以下问题：Error in xy.coords(x, y, xlabel, ylabel, log) : 'x'和'y'的长度不一样。请对原代码进行修正

在原代码中，有一处需要修改。在绘制Prediction error plot的部分，第10行的代码需要修改为：

mean((x_mat %*% predict(fit, newx = x_mat) - switch(i, y1, y2, y3))^2, na.rm = TRUE) # 修改此处

修改后的代码如下：

library(glmnet)
library(ggplot2)

# 生成5030的随机数据和30个变量
set.seed(1111)
n <- 50
p <- 30
X <- matrix(runif(n * p), n, p)
y <- rnorm(n)

# 生成三组不同系数的线性模型
beta1 <- c(rep(1, 3), rep(0, p - 3))
beta2 <- c(rep(0, 10), rep(1, 3), rep(0, p - 13))
beta3 <- c(rep(0, 20), rep(1, 3), rep(0, p - 23))
y1 <- X %*% beta1 + rnorm(n)
y2 <- X %*% beta2 + rnorm(n)
y3 <- X %*% beta3 + rnorm(n)

# 设置交叉验证折数
k <- 10

# 设置不同的lambda值
lambda_seq <- 10^seq(10, -2, length.out = 100)

# 执行交叉验证和岭回归，并记录CV error和Prediction error
cv_error <- list()
pred_error <- list()

for (i in 1:3) {
  # 交叉验证
  cvfit <- cv.glmnet(X, switch(i, y1, y2, y3), alpha = 0, lambda = lambda_seq, nfolds = k)
  cv_error[[i]] <- cvfit$cvm

  # 岭回归
  fit <- glmnet(X, switch(i, y1, y2, y3), alpha = 0, lambda = lambda_seq)
  pred_error[[i]] <- apply(X, 2, function(x) {
    x_mat <- matrix(x, nrow = n, ncol = p, byrow = TRUE)
    mean((x_mat %*% predict(fit, newx = x_mat) - switch(i, y1, y2, y3))^2, na.rm = TRUE) # 修改此处
  })
}

# 绘制图形
par(mfrow = c(3, 2), mar = c(4, 4, 2, 1), oma = c(0, 0, 2, 0))

for (i in 1:3) {
  # CV error plot
  cv_plot_data <- cv_error[[i]]
  plot(log10(lambda_seq), cv_plot_data, type = "l", xlab = expression(log10), ylab = "CV error", main = paste0("Model ", i))
  abline(v = log10(cvfit$lambda.min), col = "red")

  # Prediction error plot
  pred_plot_data <- pred_error[[i]]
  plot(log10(lambda_seq), pred_plot_data, type = "l", xlab = expression(log10), ylab = "Prediction error", main = paste0("Model ", i))
  abline(v = log10(lambda_seq[which.min(pred_plot_data)]), col = "red")
}