Installing R on Mint 17
As nearly always, when one wants to do something in Linux, it becomes a test of both intelligence and patience. Mostly the latter.
In this case I had installed the newest Mint on my new laptop, Mint 17. Then I set out to install R. Since this language's name is but a single letter, it is not so easy to search for solutions. The first question is what the linux program is called. r-base, it turns out. However, to install it, one needs to add the CRAN mirror to the repository list (sources.list file in etc/apt/). But their website is not very helpful because they don't give any examples, just write "http://<my.favorite.cran.mirror>/bin/linux/ubuntu utopic/". And if one chooses the CRAN mirror in DK, the URL is "http://mirrors.dotsrc.org/cran/". However, adding "http://mirrors.dotsrc.org/cran/bin/linux/ubuntu utopic/" does not work. Apparently, one has to know that one must remove the "/cran" part of the URL first. In any case, I ended up using "deb http://cran.at.r-project.org/bin/linux/ubuntu utopic/" which works except that it gives errors about the lack of a public key (apparently not important).
Then it's a matter of trying sudo apt-get install r-base, but no no. There are various dependencies missing. In particular, libgomp1 was in some 4.8x version, while the required version was 4.9x. So, to Synaptics I go. But according to Synaptics, I already have the latest version!
Ok, so Synaptics itself must be outdated. So I updated the source lists (sudo apt-get update) but that didn't help either. Then I tried downloading and installing libgomp1 manually, but that just required some more dependencies...
So, next idea was to update the repositories that Linux uses. Apparently, Mint 17 is based on Ubuntu 14.04 (Trusty Tahr). The question was just where one gets the URLs of these. After spending perhaps an hour trying some of the wrong ones, I finally found this page where one can generate sources.list code for Ubuntu that are updated! So I ended up with:
#deb cdrom:[Linux Mint 17 _Qiana_ - Release amd64 20140624]/ trusty contrib main non-free deb http://cran.at.r-project.org/bin/linux/ubuntu utopic/
###### Ubuntu Main Repos deb http://dk.archive.ubuntu.com/ubuntu/ utopic main restricted universe deb-src http://dk.archive.ubuntu.com/ubuntu/ utopic main restricted universe
###### Ubuntu Update Repos deb http://dk.archive.ubuntu.com/ubuntu/ utopic-security main restricted universe deb http://dk.archive.ubuntu.com/ubuntu/ utopic-updates main restricted universe deb-src http://dk.archive.ubuntu.com/ubuntu/ utopic-security main restricted universe deb-src http://dk.archive.ubuntu.com/ubuntu/ utopic-updates main restricted universe
###### Ubuntu Partner Repo deb http://archive.canonical.com/ubuntu utopic partner deb-src http://archive.canonical.com/ubuntu utopic partner
###### Ubuntu Extras Repo deb http://extras.ubuntu.com/ubuntu utopic main deb-src http://extras.ubuntu.com/ubuntu utopic main
Which worked. After running update, I could then use Synaptics to install r-base with the dependencies. Hurray!