GNU Octave, version 2.1.72 (i686-pc-cygwin). Copyright (C) 2005 John W. Eaton. This is free software; see the source code for copying conditions. There is ABSOLUTELY NO WARRANTY; not even for MERCHANTIBILITY or FITNESS FOR A PARTICULAR PURPOSE. For details, type `warranty'. Additional information about Octave is available at http://www.octave.org. Please contribute if you find this software useful. For more information, visit http://www.octave.org/help-wanted.html Report bugs to (but first, please read http://www.octave.org/bugs.html to learn how to write a helpful report). reading commands from /usr/share/octave/site/m/startup/octaverc ... done. reading commands from /usr/share/octave/2.1.72/m/startup/octaverc ... done. LOADPATH = : DEFAULT_LOADPATH = .:/usr/lib/octave/2.1.72/site/oct/i686-pc-cygwin//:/usr/lib/octave/site/oct/api-v13/i686-pc-cygwin//:/usr/lib/octave/site/oct/i686-pc-cygwin//:/usr/share/octave/2.1.72/site/m//:/usr/share/octave/site/api-v13/m//:/usr/share/octave/site/m//:/usr/lib/octave/2.1.72/oct/i686-pc-cygwin//:/usr/share/octave/2.1.72/m// which: `butter' is undefined /usr/share/octave/site/m/octave-forge/signal/butter.m DEFAULT_LOADPATH = .:/usr/lib/octave/2.1.72/site/oct/i686-pc-cygwin//:/usr/lib/octave/site/oct/api-v13/i686-pc-cygwin//:/usr/lib/octave/site/oct/i686-pc-cygwin//:/usr/share/octave/2.1.72/site/m//:/usr/share/octave/site/api-v13/m//:/usr/share/octave/site/m//:/usr/lib/octave/2.1.72/oct/i686-pc-cygwin//:/usr/share/octave/2.1.72/m//:/usr/share/octave/site/m// which: `butter' is undefined DEFAULT_LOADPATH = .:/usr/lib/octave/2.1.72/site/oct/i686-pc-cygwin//:/usr/lib/octave/site/oct/api-v13/i686-pc-cygwin//:/usr/lib/octave/site/oct/i686-pc-cygwin//:/usr/share/octave/2.1.72/site/m//:/usr/share/octave/site/api-v13/m//:/usr/share/octave/site/m//:/usr/lib/octave/2.1.72/oct/i686-pc-cygwin//:/usr/share/octave/2.1.72/m//:/usr/share/octave/site/m//:/usr/share/octave/site/m/octave-forge// butter is the user-defined function from the file /usr/share/octave/site/m/octave-forge/signal/butter.m