How do I plot Sinusoidal wave over a circle in Matlab?

Answer 1

[Arthur Reis]

I'm not sure if I 100% understood your question, but here it is

t = 0:0.01:2*pi; %define interval
x = cos(t);
y = sin(t);
figure;
plot(x,y); %normal circle
%%
f = 10; %define modulation frequency
A = .2; % modulation amplitude
R = A*cos(f*t); %
x = cos(t) + R;
y = sin(t) + R;
figure;
plot(x,y); %similar to your example
%% 
x = cos(t).*(1 + R);
y = sin(t).*(1 + R);
figure;
plot(x,y); %modulating the radius

[loyyy]

Hi, thank you for your response. It should be 3 dimensional.

[Arthur Reis]

like so?

t = 0:0.01:2*pi; %define interval
x = cos(t);
y = sin(t);
f = 10; %define modulation frequency
A = .2; % modulation amplitude
R = A*cos(f*t); %
z = R;
figure;
plot3(x,y,z); 

[loyyy]

Thank you.

[Arthur Reis]

no problem. If you could please accept an answer so we can close this quesiton.

[loyyy]

Hi @Arthur Reis! Follow up question. If I want to pick 120 points/vertices in the closed curve (equal distances) and extarct their coordinates. What will be the codes then? Hoping you could help me on this problem, as soon as possible. Thank you very much.

[Arthur Reis]

Hello,

you'll only need to change the definition of the 't'. You can use linspace to get an linearly spaced array with expecific number of points (120 in this case). So:

tp = linspace(0,2*pi,120); %new array 
xp = cos(tp);
yp = sin(tp);
f = 10; %define modulation frequency
A = .2; % modulation amplitude
Rp = A*cos(f*tp); %
zp = Rp;
figure;
scatter3(xp,yp,zp); 

Their coordinates are xp, yp, zp.

Does this solve your problem?

[loyyy]

Yes, Thank you.