How to get the fuzzy value of an input when the crisp value is given

I have implemented a fuzzy logic system using toolbox. I want to get the fuzzy value of the crisp input using matlab code. Can you please help me to do this.

Answer 1

[Sam Chak]

The evalmf() function can used in this situation.

help evalmf

  EVALMF Evaluates membership functions.
 
    Y = EVALMF(MF,X) Evaluates a type-1 MF with X to generate Y. MF is a
    scalar or vector of membership function objects and X contains numeric
    values to be evaluated by MF. 
 
    If MF
      - is a scalar, X can be a scalar, vector, or 2D matrix.
      - is a vector, X must be a scalar or vector.
 
    If MF is a scalar membership function object, the size of Y is same as
    X. In case of a linear membership function, size of Y depends on number
    of input sets specified in X.
 
    If MF is a vector, Y is a matrix of size [M N], where M and N are
    lengths of MF and X, respectively.
 
    [YU,YL] = EVALMF(MF,X) Evaluates a type-2 MF with input values X to
    generate output values YU and YL, where YU represents the evaluated
    outputs of the upper membership functions of MF and YL corresponds to
    the evaluated outputs of the lower membership functions.
 
    Examples
      %% Type-1 membership functions.
      mf = [fismf(@gaussmf,[1.5 5]) fismf(@trapmf,[3 4 6 7])];
      x = (-2:0.1:12)';
      y = evalmf(mf,x);
      plot(x,y)
      xlabel('Universe of discourse (x)'),ylabel('Type-1 membership value (y)')
      legend('gaussmf, P=[1.5 5]','trapmf, P=[3 4 6 7]')
 
      %% Type-2 membership functions.
      mf = [fismftype2(@gaussmf,[1.5 5]) fismftype2(@trapmf,[3 4 6 7])];
      x = (-2:0.1:12)';
      [yu,yl] = evalmf(mf,x);
      plot(x,[yu;yl])
      xlabel('Universe of discourse (x)'),ylabel('Type-2 Membership values (yu,yl)')
      legend('gaussmf, P=[1.5 5]','trapmf, P=[3 4 6 7]')
 
    See also
      fismf fismftype2

    Documentation for evalmf
       doc evalmf

x  = -10:0.1:10;
mf = fismf("pimf", [-9 -7 2 7]);
y  = evalmf(mf, x);

% plot membership function
plot(x, y, 'linewidth', 1.5), grid on, ylim([-0.2 1.2]); 
xlabel('\it{x}'), ylabel('\mu(\it{x})')

% find the fuzzy value when the crisp value x = 4
fuz_value = evalmf(mf, 4)

fuz_value = 0.6800

xline(4, '--', '4');
yline(fuz_value, '--', sprintf('%.4f', fuz_value));