R包下载错误

安装R包时，突然遇见如下错误

Warning in install.packages :
InternetOpenUrl failed: ''
Warning in install.packages :
InternetOpenUrl failed: ''
Warning in install.packages :
InternetOpenUrl failed: ''
Warning in install.packages :
unable to access index for repository https://mirrors.tuna.tsinghua.edu.cn/CRAN/src/contrib:
cannot open URL 'https://mirrors.tuna.tsinghua.edu.cn/CRAN/src/contrib/PACKAGES'
Installing package into ‘C:/Users/Administrator/Documents/R/win-library/3.6’
(as ‘lib’ is unspecified)
Warning in install.packages :
InternetOpenUrl failed: ''
Warning in install.packages :
InternetOpenUrl failed: ''
Warning in install.packages :
InternetOpenUrl failed: ''
Warning in install.packages :
unable to access index for repository https://mirrors.tuna.tsinghua.edu.cn/CRAN/src/contrib:
cannot open URL 'https://mirrors.tuna.tsinghua.edu.cn/CRAN/src/contrib/PACKAGES'
Warning in install.packages :
package ‘RIdeogram’ is not available (for R version 3.6.3)
Warning in install.packages :
InternetOpenUrl failed: ''
Warning in install.packages :
InternetOpenUrl failed: ''
Warning in install.packages :
InternetOpenUrl failed: ''
Warning in install.packages :
unable to access index for repository https://mirrors.tuna.tsinghua.edu.cn/CRAN/bin/windows/contrib/3.6:
cannot open URL 'https://mirrors.tuna.tsinghua.edu.cn/CRAN/bin/windows/contrib/3.6/PACKAGES'
Warning message:
R graphics engine version 12 is not supported by this version of RStudio. The Plots tab will be disabled until a newer version of RStudio is installed.

解决方法：

https://blog.csdn.net/xiangyong58/article/details/51980592

R语言镜像访问貌是通过IE浏览器，所以查看IE浏览器是否可以连上网，往往问题出在IE浏览器不能连网。将IE浏览器重新修复(方法参照百度)后加载安装包就能成功运行了，顺利加载。

IE浏览器重新修复：

https://jingyan.baidu.com/article/22fe7ced616e463002617f35.html