当我尝试使用此命令安装Rcmdr软件包时：
install.packages("Rcmdr",dependencies=TRUE)
我收到以下错误消息：
trying URL 'http://cran.csiro.au/bin/windows/contrib/3.1/Rcmdr_2.1-1.zip'
Error in download.file(url, destfile, method, mode = "wb", ...) :
cannot open URL 'http://cran.csiro.au/bin/windows/contrib/3.1/Rcmdr_2.1-1.zip'
In addition: Warning message:
In download.file(url, destfile, method, mode = "wb", ...) :
cannot open: HTTP status was '404 Not Found'
Warning in download.packages(pkgs, destdir = tmpd, available = available, :
download of package ‘Rcmdr’ failed
请有人帮我解决这个问题。