Question: I want to install Octave on my Ubuntu LTS with `apt-get`. The problem is that the official repositories list only Octave 3.0 and Octave 3.2, whereas the latest Octave is Octave 3.6.

How do I update the repositories of apt-get to get Octave 3.6?

Answer: 
[This PPA](https://launchpad.net/%7Epicaso/+archive/octave) should solve your problem, provided you are running the latest 12.04.

Open Terminal `Ctrl-Alt-T` and type:

```

sudo apt-add-repository -y ppa:picaso/octave
sudo apt-get update 
sudo apt-get install octave
sudo apt-get install liboctave-dev 

```

---

For Ubuntu 20.04, see [this](https://askubuntu.com/a/206050/124466) answer.
Just as an update: [this PPA](https://launchpad.net/~mtmiller/+archive/octave) (maintained by a member of the Debian Octave Group) provides the latest Octave for a range of Ubuntu versions.