RStudio,install包下载失败

> install.packages("rmda")

Warning in install.packages :   unable to access index for repository https://cran.rstudio.com/src/contrib:  

cannot open URL 'https://cran.rstudio.com/src/contrib/PACKAGES'

Warning in install.packages :   unable to access index for repository https://cran.rstudio.com/src/contrib:  

cannot open URL 'https://cran.rstudio.com/src/contrib/PACKAGES'

Warning in install.packages :   package ‘scatterplot3d’ is not available (for R version 3.5.1)

Warning in install.packages :   unable to access index for repository https://cran.rstudio.com/bin/windows/contrib/3.5:  

cannot open URL 'https://cran.rstudio.com/bin/windows/contrib/3.5/PACKAGES'

Warning: unable to access index for repository https://cran.rstudio.com/src/contrib:   cannot open URL 'https://cran.rstudio.com/src/contrib/PACKAGES'

> update.packages()
Warning: 无法在貯藏處https://mirrors.tongji.edu.cn/CRAN/src/contrib中读写索引:
  无法打开URL'https://mirrors.tongji.edu.cn/CRAN/src/contrib/PACKAGES'
> options(repos='http://cran.rstudio.com/')
> install.packages("rmda")

可以了

参考来源：

原文链接：https://blog.youkuaiyun.com/u013303361/article/details/85344742