# I need help with fourier matrix index integral, I can't find how to write it in matlab

2 views (last 30 days)
Mircea Mircea on 8 May 2022
Commented: Mircea Mircea on 8 May 2022
I don't know how to type this into matlab. Fourier function with matrix index
Here is my mathcad code and I'm trying to learn how to write it in matlab: The first part of my matlab code is i which corresponds with i(t) from mathcad photo. I can't find how to write the integral with matrice index.
%%
%current i(t)
T=20*10^-3;
t=0:T/1000:T;
w=2*pi*1/T;
i=100.*(t>1*T/12).*(t<5*T/12)-100.*(t>7*T/12).*(t<11*T/12);
u=sin(w*t).*10.*(t>0).*(t<T);
%plot i
figure(1)
plot(t,i, 'DisplayName', 'i(t)')
hold on
legend
xlabel('Time','FontSize',16)
title('3.20','FontSize',16)
%until here the code is working
%a0, an, ab
n = linspace(0, 50);
T=20*10^-3;
t=0:T/1000:T;
w=2*pi*1/T;
a0 = @(i,T) integral(@(t) 2./T.*i, 0, T);
an = @(i,T) integral(@(t) 2./T.*i.*cos(n*w*t), 0, T);
ab = @(i,T) integral(@(t) 2./T.*i.*sin(n*w*t), 0, T);
F=sum(an.*cos(n*w*t).+bn.*sin(n*w*t)
fourier=(a0/2)+F
%plot fourier + current
figure(2)
plot(t,i+fourier, 'DisplayName', 'fourier')
hold on
legend
xlabel('Time','FontSize',16)
title('3.20','FontSize',16)
It should plot like this: Any help is appreciated thanks.
Torsten on 8 May 2022
You might want to learn MATLAB's basics here:

Torsten on 8 May 2022
Edited: Torsten on 8 May 2022
n = 50;
T=20*10^-3;
t=0:T/1000:T;
w=2*pi*1/T;
f=@(t)0+100.*(t>1*T/12).*(t<5*T/12)-100.*(t>7*T/12).*(t<11*T/12);
a0 = 2/T*integral(@(t)f(t),0,T);
for i=1:n
a(i) = 2/T*integral(@(t)f(t).*cos(w*i*t),0,T);
b(i) = 2/T*integral(@(t)f(t).*sin(w*i*t),0,T);
end
four = @(t) a0/2+sum((a(1:n).*cos((1:n)*w*t)+b(1:n).*sin((1:n)*w*t)));
four_eval = arrayfun(four,t)
plot(t,f(t))
hold on
plot(t,four_eval)
Mircea Mircea on 8 May 2022
Thank you very much! Also thank you for the link provided!

R2020b

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!