# How to create membership functions matlab in triangular form?

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mindo akami on 9 Jun 2021
Edited: Sam Chak on 22 Mar 2022
Hi, hoping somone can help
i add the rule 1 and 2 with trimf function but how can i plot the rule 3 and 4 pleas (see the attched images) thanks )

darova on 9 Jun 2021
Use sine wave
x = 0:pi/2:20;
y = sin(x);
plot(x,y)
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darova on 24 Jul 2021
Maybe manual solution?
x = [-180 -90 -90 90 90 180];
y = abs(sind(x));
y(3:4) = 0;
plot(x,y)

Sam Chak on 22 Mar 2022
Edited: Sam Chak on 22 Mar 2022
You probably have already learned the manual way to plot these. Since this is unanswered and if you are still interested in learning to plot the 'fuzzy way', here is the code:
x = -180:0.1:180; % set the domain of discourse
y1 = trimf(x,[-90 0 90]); % Rule 1
y2 = 1 - y1; % Rule 2
y3 = trimf(x,[-180 -90 -90]) + trimf(x,[90 90 180]); % Rule 3
y4 = trimf(x,[-180 -180 -90]) + trimf(x,[90 180 180]); % Rule 4
h = plot(x, y1, 'r-', x, y2, 'g-', x, y3, 'b-', x, y4, 'm-');
set(h, 'LineWidth', 1.5)
xticks([-180 -90 0 90 180]);
xlabel('x_{1}, (degree)');
ylabel('Degree of Membership, \mu');
The line colors follow the original image that you posted here:
Result: