fuz_mul.m

FISMAT accommodates different arithmetic operators, fuzzification and defuzzification algorithm, imp

function f = fuz_mul(f1,f2)

% f=fuz_mul(f1,f2)
%
% Multiplication of two fuzzy intervalls (numbers) in LR-representation.
% (approximation - Dubois and Prade).
% The formula is as more precise as "sharper" the numbers are.
% Both numbers can have the same or different sign.
% f=f1=f2 = [xmin xmax m n alpha beta]
% Condition ymin=0 and ymax=1 .
%
% f = [xmin, xmax, m1*m2, n1*n2, m1*alpha2+m2*alpha1-alpha1*alpha2,
%      n1*beta2+n2*beta1+beta1*beta2 ] 
% 
% for f1=f2=positive. (for different signs, first signreversal)
%
% FSTB - Fuzzy Systems Toolbox for MATLAB
% Copyright (c) 1993-1996 by Olaf Wolkenhauer
% Control Systems Centre at UMIST
% Manchester M60 1QD, UK
%
% 8-Feb-1994

if (fuz_sign(f1) | fuz_sign(f2)) == 3;
  error('Error: one (LR-) intervall (number) zero. fuz_mul impossible !');
end;
if fuz_sign(f1) == 1;          % if f1 positive
  if fuz_sign(f2) == 1;        % and  f2 positive
    f=fuz_mul1(f1,f2);         % f  = f1 * f2
  else                         % if f1 positive and f2 negative
    f2=fuz_sire(f2);           % f2 = -f2
    f =fuz_mul1(f1,f2);        % f  = f1 * -f2
    f =fuz_sire(f);            % f  = -f
  end;
else                           % if f1 negative
  if fuz_sign(f2) == 1;        % and  f2 positive
    f1=fuz_sire(f1);           % f1 = -f1
    f =fuz_mul1(f1,f2);        % f  = -f1 * f2
    f =fuz_sire(f);            % f  = -f
  else                         % if f1 and f2 negative
    f1=fuz_sire(f1);           % f1 = -f1
    f2=fuz_sire(f2);           % f2 = -f2
    f =fuz_mul1(f1,f2);        % f  = -f1 * -f2
  end;
end;