Packages problems

Hi!

I also have problems when I try to install packages. I use R (v. 3.3.0) on
iMac (v. 10.11.4).
For instance:

install.packages("doBy")

Warning: unable to access index for repository
http://ftp.sunet.se/pub/lang/CRAN/src/contrib:
  cannot open URL 'http://ftp.sunet.se/pub/lang/CRAN/src/contrib/PACKAGES'
Warning: unable to access index for repository
http://ftp.sunet.se/pub/lang/CRAN/bin/macosx/mavericks/contrib/3.3:
  cannot open URL '
http://ftp.sunet.se/pub/lang/CRAN/bin/macosx/mavericks/contrib/3.3/PACKAGES'
Warning message:
package ?doBy? is not available (for R version 3.3.0)

But when I give the same command using RStudio, everything works just fine

install.packages("doBy")

trying URL '
https://cran.rstudio.com/bin/macosx/mavericks/contrib/3.3/doBy_4.5-15.tgz'
Content type 'application/x-gzip' length 3429051 bytes (3.3 MB)
==================================================
downloaded 3.3 MB

Also, the Get list button on the R Package Intaller window generates an
error message

Warning: unable to access index for repository
http://ftp.sunet.se/pub/lang/CRAN/bin/macosx/mavericks/contrib/3.3:
  cannot open URL '
http://ftp.sunet.se/pub/lang/CRAN/bin/macosx/mavericks/contrib/3.3/PACKAGES'