用.libPath()命令查看或指定包的安装路径，通常来说，临时下载的包在安装后会提示安装在C:/Program ...
用.libPath()命令查看或指定包的安装路径，通常来说，临时下载的包在安装后会提示安装在C:/Program Files/R/R-3.3.1/library