下载scatterplot3d.package出现问题如下：
trying URL 'http://cran.rstudio.com/bin/macosx/contrib/3.0/scatterplot3d_0.3-35.tgz'
Error in download.file(url, destfile, method, mode = "wb", ...) :
  cannot open URL 'http://cran.rstudio.com/bin/macosx/contrib/3.0/scatterplot3d_0.3-35.tgz'
In addition: Warning message:
In download.file(url, destfile, method, mode = "wb", ...) :
  cannot open: HTTP status was '500 Internal Server Error'
Warning in download.packages(pkgs, destdir = tmpd, available = available,  :
  download of package 'scatterplot3d' failed

求大神指点，感激不尽！