R 错误：“contrib.url（repos，“source”）中的错误：尝试在不设置镜像的情况下使用 CRAN……”

Question

Error in contrib.url(repos, "source") : 
  trying to use CRAN without setting a mirror
Calls: <Anonymous> ... eval_with_user_handlers -> eval -> eval -> install.packages -> contrib.url
Execution halted

我尝试安装 ggplot 但没有成功