报错内容如下：

"Warning in install.packages :  cannot open URL 'http://www.stats.ox.ac.uk/pub/RWin/src/contrib/PACKAGES.rds': HTTP status was '404 Not Found'Installing package into ‘C:/Users/cxy/Documents/R/win-library/3.4’(as ‘lib’ is unspecified)Warning in install.packages :  cannot open URL 'http://www.stats.ox.ac.uk/pub/RWin/bin/windows/contrib/3.4/PACKAGES.rds': HTTP status was '404 Not Found'trying URL 'https://mran.microsoft.com/snapshot/2017-10-15/bin/windows/contrib/3.4/stringi_1.1.5.zip'Content type 'application/zip' length 14289948 bytes (13.6 MB)downloaded 13.6 MBpackage ‘stringi’ successfully unpacked and MD5 sums checkedThe downloaded binary packages are in        C:\Users\cxy\AppData\Local\Temp\RtmpmCCuF0\downloaded_packages"


虽然能下载成功，但是有什么办法可以直接从微软镜像下载就好，略过打开

http://www.stats.ox.ac.uk/pub/RWin……这一步