我可以提前安装一些软件包，但最近我无法安装任何软件包，也无法更新软件包。 例如，每次我尝试使用
安装“预测”包时install.packages("forecast")
，我收到以下消息：
Installing package into ‘C:/Users/Ge/Documents/R/win-library/3.3’
(as ‘lib’ is unspecified)
also installing the dependencies ‘quadprog’, ‘tseries’, ‘fracdiff’,‘RcppArmadillo’
Packages which are only available in source form, and may need
compilation of C/C++/Fortran: ‘quadprog’ ‘tseries’ ‘fracdiff’
‘RcppArmadillo’ ‘forecast’
These will not be installed
我尝试使用
更换镜像chooseCRANmirror()
它无法正常工作。 请有人帮帮我