I wrote about this before, but since this is a frequent problem and my last post wasn't brief, here's a shorter version. The primary way to install software in Linux is to rely on apt-get (apt in Mint) or some other package manager. The way this works is that there is a central server which holds a list of all the software available for that version of Linux you installed. The problem is that your installed version of Linux is based on an older list of this software and thus when you try to update, it says there isn't any newer version available when there actually is.
Installing the latest version of R on Ubuntu/Mint
Installing the latest version of R on…
Installing the latest version of R on Ubuntu/Mint
I wrote about this before, but since this is a frequent problem and my last post wasn't brief, here's a shorter version. The primary way to install software in Linux is to rely on apt-get (apt in Mint) or some other package manager. The way this works is that there is a central server which holds a list of all the software available for that version of Linux you installed. The problem is that your installed version of Linux is based on an older list of this software and thus when you try to update, it says there isn't any newer version available when there actually is.