I installed Octave 3.2 for Slackware 12.2 on Slackware 13. Octave for 13 isn't available.
Octave initially didn't run correctly. I did need to do one fix. Octave 3.2 for Slackware 12.2 needs libgfortran.so.2.0.0.
The fix is (as root) to add a soft link from /usr/lib/libgfortran.so.3.0.0. to /usr/lib/libgfortran.so.2
$ ls -l /usr/lib/libgfortran.so.2
lrwxrwxrwx 1 root root 20 2009-09-16 12:31 /usr/lib/libgfortran.so.2 -> libgfortran.so.3.0.0
Octave 3.2 for Slackware 12.2 is available from Slacky.eu at:
Note the dependencies, more dependent packages are needed.