How+can+I+use+Weka+with+Matlab+or+Octave?

Matlab and Octave allow you to interface with Java applications, which allows you to use Weka from within these applications.

See the following presentation, section //Octave// (Octave is fairly compatible with Matlab), on how to use the Java integration: http://www.cs.waikato.ac.nz/~eibe/WEKA_Ecosystem.pdf