The graph or output values from the surface viewer on the Fuzzy Logic App are actually defuzzified output values.
fis = mamfis('Name', "Test_FIS");
% Fuzzy Input #1
fis = addInput(fis, [-1 1], 'Name', 'E');
fis = addMF(fis, 'E', 'zmf', [-0.5 0.25], 'Name', 'N');
fis = addMF(fis, 'E', 'gaussmf', [0.25 0], 'Name', 'Z');
fis = addMF(fis, 'E', 'smf', [-0.25 0.5], 'Name', 'P');
% Fuzzy Output
fis = addOutput(fis, [-1 1], 'Name', 'U');
fis = addMF(fis, 'U', 'zmf', [-0.5 0.25], 'Name', 'N');
fis = addMF(fis, 'U', 'gaussmf', [0.25 0], 'Name', 'Z');
fis = addMF(fis, 'U', 'smf', [-0.25 0.5], 'Name', 'P');
% Plot Membership functions
figure(1)
subplot(2,1,1)
plotmf(fis, 'input', 1), grid on, title('Input')
subplot(2,1,2)
plotmf(fis, 'output', 1), grid on, title('Output')
% Fuzzy Rules
rules = [...
"E==N => U=N"; ...
"E==Z => U=Z"; ...
"E==P => U=P"; ...
];
fis = addRule(fis, rules);
% Generate output of Mamdani FIS
figure(2)
opt = gensurfOptions('NumGridPoints', 201);
gensurf(fis, opt), grid on
hold on
input_E = [0.5 -0.5];
output_U = evalfis(fis, input_E)
q = plot(input_E, output_U, 'o', 'MarkerSize', 10);
q.LineWidth = 1.5;
