新手小白，为了完成毕业论文，从网上找的循环作图代码，改了一下之后运行就报错了，不知道问题出在哪里，还请各位大佬指点！

报错：错误: Aesthetics must be either length 1 or the same as the data (4): x
代码如下：
setwd("C:\\Users\\DELL\\Desktop")
library(ggplot2)
bohaibay <- read.table("C:/Users/DELL/Desktop/test217.csv", header = TRUE, sep = ",")
# Make plots.
plot_list = list()
for (i in 1:10) {
  new <- bohaibay[which(bohaibay$id == i), ]
  year = new[,3]
  avg = new[,4]
  p = ggplot(new, aes(x=year,y=avg)) +
    geom_line()
  plot_list[] = p
}
# Save plots to tiff. Makes a separate file for each plot.
for (i in 1:10) {
  file_name = paste("bohaibay_plot_", i, ".tiff", sep="")
  tiff(file_name)
  print(plot_list[])
  dev.off()
}
*在此处报错
# Another option: create pdf where each page is a separate plot.
pdf("plots9.pdf")
for (i in 1:10) {
  print(plot_list[])
}
*在此处报错
dev.off()