如何使用r中的dplyr应用loess函数并按组获取预测？

# 安装并加载必要的包
if (!require("dplyr")) install.packages("dplyr")
if (!require("ggplot2")) install.packages("ggplot2")

library(dplyr)
library(ggplot2)

# 创建一个示例数据集
set.seed(123)
df <- data.frame(
  group = rep(letters[1:5], each = 20),
  x = runif(100, 0, 100),
  y = rnorm(100, mean = 50 + 2 * x, sd = 10)
)

# 使用dplyr按组应用loess并获取预测值
df_loess <- df %>%
  group_by(group) %>%
  do({
    loess_mod <- loess(y ~ x, data = .)
    data.frame(x = seq(min(.$x), max(.$x), length.out = 100),
                yhat = predict(loess_mod, newdata = data.frame(x = seq(min(.$x), max(.$x), length.out = 100))))
  }) %>%
  ungroup()

# 查看结果
head(df_loess)

# 可视化结果
ggplot() +
  geom_point(data = df, aes(x = x, y = y, color = group)) +
  geom_line(data = df_loess, aes(x = x, y = yhat, color = group), size = 1) +
  theme_minimal()