Overhaul interp1, interp2, interp3 functions. * NEWS: Announce change in 'cubic' interpolation method for interp2 to match Matlab. * bicubic.m: Use interp2 (..., "spline") in %!tests. * interp1.m: Improve docstring. Use switch statement instead of if/elseif tree for simpler code. Use more informative error message than 'table too short'. Add titles to demo plots. Add new demo block showing difference between 'pchip' and 'spline' methods. * interp2.m: Rewrite docstring. Use variable 'extrap' instead of 'extrapval' to match documentation. Use clearer messages in error() calls. Make 'cubic' use the same algorithm as 'pchip' for Matlab compatibility. Use Octave coding conventions regarding spaces between variable and parenthesis. Added input validation tests. * interp3.m: Rewrite docstring. Use clearer messages in error() calls. Make 'cubic' use the same algorithm as 'pchip' for Matlab compatibility. Simplify input processing. Rewrite some %!tests for clarity. Added input validation tests.

syntax: regexp
# The recurrent (^|/) idiom in the regexps below should be understood
# to mean "at any directory" while the ^ idiom means "from the
# project's top-level directory".

# gnulib makes these silly backup files
.~$

# This directory gets created by gnulib during the build. 
# It contains no Octave files.
^libgnu/*

# This directory mostly contains cruft during build time, but it does
# contain some Octave code, so we gotta be a bit more careful about
# what we ignore here
^m4/(?!ax_).+\.m4$

# Emacs tools create these
(^|/)TAGS$
(^|/)semantic.cache$

(/|^)Makefile\.in$
^INSTALL$

^aclocal\.m4$
^build-.*($|/)
^configure$
^autom4te\.cache($|/)
^config\.in\.h$

# e.g. doc/faq/OctaveFAQ.info
#      doc/interpreter/octave.info-4
^doc/.*\.info(-\d)?$

^doc/\w*/stamp-vti$
^doc/\w*/version\.texi$
^doc/interpreter/images\.mk$

# e.g. liboctave/operators/smx-op-inc.mk
^liboctave/operators/\w+-op-\w+\.mk$

^libinterp/dldfcn/module\.mk$