How do you install the latest version of GNU Octave?

You can install the latest stable version of GNU Octave for any supported Ubuntu release:

sudo apt-add-repository ppa:octave/stable
sudo apt-get update
sudo apt-get install octave

This PPA is maintained and supported by several Octave developers.

For octave 3.6.1

sudo add-apt-repository ppa:picaso/octave
sudo apt-get update ; sudo apt-get install octave

Yes you can get octave-3.6.3 , open your terminal and paste this

wget ftp://ftp.gnu.org/gnu/octave/octave-3.6.3.tar.bz2
tar -xvf octave-3.6.3.tar.bz2
cd octave-3.6.3
./configure
 make
 sudo make install 

Hope that helps :D

Ubuntu 12.04.3 and Octave 3.8.0 with statistics

wget ftp://ftp.gnu.org/gnu/octave/octave-3.8.0.tar.bz2
tar -xvf octave-3.8.0.tar.bz2
cd octave-3.8.0
sudo apt-get build-dep octave
./configure
make
sudo make install

sudo apt-get install octave-statistics
octave
pkg install -forge io
pkg install -forge statistics
pkg load statistics