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## Copyright (C) 2011-2025 L. Markowsky <lmarkowsky@gmail.com>
##
## This file is part of the fuzzy-logic-toolkit.
##
## The fuzzy-logic-toolkit is free software; you can redistribute it
## and/or modify it under the terms of the GNU General Public License
## as published by the Free Software Foundation; either version 3 of
## the License, or (at your option) any later version.
##
## The fuzzy-logic-toolkit is distributed in the hope that it will be
## useful, but WITHOUT ANY WARRANTY; without even the implied warranty
## of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
## General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with the fuzzy-logic-toolkit; see the file COPYING. If not,
## see <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Script File} {} cubic_approx_demo
##
## Demonstrate the use of the Octave Fuzzy Logic Toolkit to approximate a
## non-linear function using a Sugeno-type FIS with linear output functions.
##
## The demo:
## @itemize @bullet
## @item
## reads an FIS structure from a file
## @item
## plots the input membership functions
## @item
## plots the (linear) output functions
## @item
## plots the FIS output as a function of the input
## @end itemize
##
## @seealso{heart_disease_demo_1, heart_disease_demo_2, investment_portfolio_demo, linear_tip_demo, mamdani_tip_demo, sugeno_tip_demo}
## @end deftypefn
## Author: L. Markowsky
## Keywords: fuzzy-logic-toolkit fuzzy tests demos
## Directory: fuzzy-logic-toolkit/inst
## Filename: cubic_approx_demo.m
## Last-Modified: 4 Jun 2024
## Read the FIS structure from a file.
fis = readfis ('cubic_approximator.fis');
## Plot the input membership functions and linear output functions.
plotmf (fis, 'input', 1);
plotmf (fis, 'output', 1, -150, 150);
## Plot the FIS output y as a function of the input x.
gensurf (fis);
%!test
%! fis = readfis ('cubic_approximator.fis');
%! cubes = evalfis([-2.5; -2; -1.5; -1; 0; 1; 1.5; 2; 2.5], fis, 101);
%! expected_result = ...
%! [-13.7500
%! -8.0000
%! -2.2500
%! -1.0000
%! 0
%! 1.0000
%! 2.2500
%! 8.0000
%! 13.7500];
%! assert(cubes, expected_result, 1e-4);
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