# Plot Fourier Series on MatLab

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Erick Samayoa on 6 Apr 2020
Answered: Asvin Kumar on 10 Apr 2020
Trying to plot the first few terms of my fourier series function but I cant seem to resemble the original function for n values greater than two.
n=[2:2:12]; % define n as only even numbers
for f=1:length(n) % define f
for Time=1:length(t)
a_not=1/pi;
b_n=(1/2)*sin((pi*t(Time))/T);
fourier(Time)=a_not+b_n+sum((2/(pi*(1-n(f)^2)))*cos((n(f)*pi*t(Time))/T));
end
figure(2)
plot(t,fourier,t,y)
hold on
end

#### 1 Comment

darova on 6 Apr 2020
You don't use ifi statement?

Asvin Kumar on 10 Apr 2020
Your coefficients are right. The issue is that instead of adding the n-th cosine to the exiting variable ‘fourier’, you were overwriting it. Here’s a simpler, stripped down and vectorized version of your code:
n=2:2:12; % define n as only even numbers
a_not=2/pi;
b1 = 0.5;
fourier = a_not/2*ones(size(t)) +b1*sin(pi*t/T) ;
for f=1:length(n) % define f
fourier = fourier + 2 / (pi*(1-n(f)^2)) * cos(n(f)*pi*t/T);
end
plot(t,fourier)
If you’re looking for a simpler way to do this have a look at the example at https://www.mathworks.com/help/curvefit/fourier.html#FitFourierModelsExample-1