Why is my plot shaking but not plotting the noise?

clear;

clc;

for x = 0:(pi/200):(2*pi)

e = rand;

y = x*sin(x)+(0.5*e);

x_star = [0:(pi/200):(2*pi)].';

y_star = x_star.*sin(x_star)+0.5*e;

figure(1)

plot(x_star,y_star)

grid on

title('Hw1');

xlabel('x');

ylabel('f(x)');

end

Answer 1

[Arif Hoq]

x = 0:pi/200:(2*pi);% does't need
e = rand;   % does't need
y = x.*sin(x)+(0.5*e); % does't need
x_star = 0:(pi/200):(2*pi); %  x_star and x same 
y_star = x_star.*sin(x_star)+0.5*rand(size(x_star)); % adding noise 0.5*rand(size(x))   y_star and y same 
figure(1)
plot(x_star,y_star)
grid on
title('Hw1');
xlabel('x');
ylabel('f(x)');

[Arif Hoq]

Or simply

x = 0:pi/200:(2*pi);
e = 0.5*rand(size(x)); % noise
y = x.*sin(x)+e;
figure(1)
plot(x,y)
grid on
title('Hw1');
xlabel('x');
ylabel('f(x)');

[Jorge Arturo Clares Pastrana]

thanks, its exactly what i was looking for