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Here are some non-obvious things I learned about Octave.

1) It is easy to generate all N! permutations of the N elements of a vector X. Use

>P = perms(X)

The permutations don’t come out in lexicographic order unfortunately.

2) Typing “whos” gives a list of all variables and built-in functions. By default, Octave uses the UNIX “less” pager to show output. This has the unfortunate effect of clearing the screen after the last item has been displayed (and you press “f”). You can avoid using “less” by typing

> more off

This can go into your startup script “octaverc”, which resides in a Windows installation in the folder

C:\Program Files\Octave\share\octave\site\m\startup

Installing Octave for Linux is easy if there is a RPM or similar package. However, I couldn’t find one for my Linux distrubtion, OpenSuSe (10.2).

I decided to roll up my sleeves and compile it. It took me a while to figure out how. Here’s what I ended up doing.

1) Install “compat-g77″ to allow Fortran 77 compilation. Download the rpm from this ftp site.

Then, as root, type “rpm -i rpmfilename”

This is the only step that was not obvious, at least not to me. I tried various other ways to install a Fortran compiler, namely “gfortran”, “g95″, and also rebuilding “gcc” from scratch. None of that is necessary. Just install the RPM, and have Fortran 77 on your system.

2) Install Gnuplot 4.2 from

http://www.gnuplot.info/download.html

The procedure for this installation, and for the others described below, is the same in each case.

• tar zxvf tarfilename
• cd directorynameofpackage
• configure
• make
• make check
• make install # as root

3) Install “FFTW”, “GMP”, “MPFR”, and “GLPK”. Look each of these up on Google and download the tarballs. Install these as in step 2.

4) Download the Octave source tarball, and install as in step 2. This will take about a hour, depending on your machine.

Octave is a public domain version of MATLAB. It is probably 70% compatible with MATLAB, which is close enough for educational purposes. Version 3.0 is a major update to Octave, with many new graphics and image processing capabilities.

The windows installer is simple and effective. I selected the JHandles options, meaning graphics is handled by the JAVA and Open-GL based “JHandles” package.

Here is the sombero plot that serves as Octave’s logo. To generate it, use

>sombrero(32),title(’sombrero(32)’);