How to fix errors when evaluating a Fuzzy System using custom membership functions

Hi.

Can anyone help me with fixing these error? I really dont know what to do.

Incorrect size for expression '<output of feval>': expected [1x:?] but found [101x1].

Error in evaluateNonhomogenousFIS_double_mex

Error in fuzzy.internal.utility.evalfis (line 97)

[varargout{1:nargout}] = fuzzy.internal.codegen. ...

Error in evalfis (line 98)

[varargout{1:nargout}] = fuzzy.internal.utility.evalfis(varargin{:});

Error in ruleview (line 427)

[v,irr,orr,arr,rfs,orrSug] = evalfis(fis,inputVector,options);

Error in ruleview (line 306)

ruleview #update

Error in fisgui (line 100)

eval([tag '(fis);']);

Error while evaluating Menu Callback.

I wrote a custom membership function based on an example, and used them in the Membership Function Editor:

function out = stairsfn(x,params)
    if params(1) == 1
    v = 0;
    else 
        v = 1;
    end
    for i = 1:length(x)
        y(i) = 0;
        if params(1) ~= 1
            y(i) = 1;
        end
        if x(i) <= (params(2)+ 2) && x(i) >= (params(2))
            v = y(i)+0.5;
            if params(1) ~= 1
                v = y(i)-0.5;
            end
            y(i) = v;
        elseif x(i) <= (params(3)+ 2) && x(i) >= (params(3))
            v = y(i)+1;
            if params(1) ~= 1
                v = y(i)-1;
            end
            y(i) = v;
        elseif x(i) >= (params(3)+ 2)
            y(i) = 1;
            if params(1) ~= 1
                y(i) = 0;
            end
        else
            y(i) = v;
        end
    end
    out = y';
    %fprintf('out %.4f \n', out);
end

In the Editor, the functions display the expected staircase graphs, http://prntscr.com/set2jy .

But when I added the fuzzy rules in the Editor, the errors appeared, http://prntscr.com/set303 .

[Sam Chak]

I have tested the stairsfn() function, which I named mf2_o in the editor. I also inserted my staircase function (mf1_s), highlighted with a bold red line in the editor, for comparison purposes. Two rules have been successfully added:

• Rule 1: If input1 is mf1_s, then output1 is mf1.
• Rule 2: If input1 is mf2_o, then output1 is mf2.

When the Rule Viewer is opened, Rule 2 is not triggered for unknown reasons, despite the input value of 200 applied to mf2_o, which should have resulted in a firing strength of 0.5. Only Rule 1 is triggered correctly, causing the centroid to incorrectly shift to output1 = -1.

Answer 1

[Sam Chak]

Hi @Oleksandr Rynas

Designing custom membership functions can be enjoyable and provide a sense of satisfaction to fuzzy logic aficionados. However, using conditional statements and for-loops can be challenging. Therefore, I typically prefer elementary mathematical functions, as they are sufficient for most applications. Both of my Heaviside-based staircase membership functions (stairsmf & stairzmf) work well in the Fuzzy System Editor.

x   = linspace(0, 400, 4001)';
mf1 = stairzmf(x, [125, 275]);
mf2 = stairsmf(x, [125, 275]);

figure
plot(x, [mf1, mf2]), grid on, ylim([-0.2, 1.2])
text( 50, 1.1, 'mf1')
text(325, 1.1, 'mf2')
xlabel('x'), ylabel('Degree of membership')
title('My Staircase membership functions')

%% S-shaped Staircase function
function out = stairsmf(x, params)
    stairs1 = 0.5*heaviside(x - params(1));
    stairs2 = 0.5*heaviside(x - params(2));
    out     = stairs1 + stairs2;
end

%% Z-shaped Staircase function
function out = stairzmf(x, params)
    stairs1 = 0.5*(1 - heaviside(x - params(1)));
    stairs2 = 0.5*(1 - heaviside(x - params(2)));
    out     = stairs1 + stairs2;
end

My Staircase functions