plot exponential Fourier series !!

Hi, my instructor asked me to plot exponential Fourier series as homework, my homework say ( plot exponential Fourier series from -N to N and with amplitude A, the program will plot figure when N = 1 then for N=2 to N = value that user input it ) but I have problem in my code the problem is : when I put the limits of summation from -N to N it doesn't work except if I put step of for loop two, but if I but it one it doesn't work. please look to my code to understand line 13, this is my code :

clear;                            
clf;                               
A = input('Enter Ampitude A :   ');
M = input('Enter limts of Summation N, where Summation limes -N:N :   ');
T0 = 2;
wo = 2*pi/T0;                          
c0 = 0;                            
for i = 0:M
N = i;
t = -5:0.01:5;                     
figure(1)                          
y = c0*ones(size(t));            
for n = -N:2:N,      %<<<<<<<<<<<<<<<  the problem is here, it can't be ( -N:1:N ) or ( -N:N )             
  cn = 2/(1j*n*wo);                 
  y = y + A*real(cn*exp(1j*n*wo*t)); 
end
cla;
P = T0/2;
plot([-5 -4 -4 -3 -3 -2 -2 -1 -1  0 0  1 1 2 2 3 3 4 4 5],...    
     [-A -A A A  -A -A  A  A -A -A A A -A -A A A -A -A A A], ':');
hold;
plot(t,y);         
xlabel('t (seconds)'); ylabel('y(t)');
ttle = ['Exponential Fourier Series with N = ',...
         num2str(N)];
title(ttle);
hold;
pause(0.5);
end

[Neptune16]

hello. can you please explain what is use for this lines?

y = c0*ones(size(t));            
for n = -N:2:N,      %<<<<<<<<<<<<<<<  the problem is here, it can't be ( -N:1:N ) or ( -N:N )             
  cn = 2/(1j*n*wo);                 
  y = y + A*real(cn*exp(1j*n*wo*t)); 

Answer 1

[Baltam]

It's because you are dividing by zero. When n = 0 then cn is infinity. Because of that, matlab can't plot your result.

If you do n = -N:2:N you don't have this problem if N is odd.

Try using:

nvec = [-N:-1:-1,1:N];
for n = nvec     %<<<<<<<<<<<<<<<  the problem is here, it can't be ( -N:1:N ) or ( -N:N )             
  cn = 2/(1j*n*wo);                 
  y = y + A*real(cn*exp(1j*n*wo*t)); 
end

in your code. This leaves out the zero-frequency component.

[yazeed Alshorman]

thank you :) Baltam

Answer 2

[Muhammad Shoaib]

clear;

clf;

A = input('Enter Ampitude A : ');

M = input('Enter limts of Summation N, where Summation limes -N:N : ');

T0 = 2;

wo = 2*pi/T0;

c0 = 0;

for i = 0:M

N = i;

t = -5:0.01:5;

figure(1)

y = c0*ones(size(t));

for n = -N:2:N, %<<<<<<<<<<<<<<< the problem is here, it can't be ( -N:1:N ) or ( -N:N )

cn = 2/(1j*n*wo);

y = y + A*real(cn*exp(1j*n*wo*t));

end

cla;

P = T0/2;

plot([-5 -4 -4 -3 -3 -2 -2 -1 -1 0 0 1 1 2 2 3 3 4 4 5],...

[-A -A A A -A -A A A -A -A A A -A -A A A -A -A A A], ':');

hold;

plot(t,y);

xlabel('t (seconds)'); ylabel('y(t)');

ttle = ['Exponential Fourier Series with N = ',...

num2str(N)];

title(ttle);

hold;

pause(0.5);

end

Answer 3

[Aman]

clear; clf; A = input('Enter Ampitude A : '); M = input('Enter limts of Summation N, where Summation limes -N:N : '); T0 = 2; wo = 2*pi/T0; c0 = 0; for i = 0:M N = i; t = -5:0.01:5; figure(1) y = c0*ones(size(t)); for n = -N:2:N, %<<<<<<<<<<<<<<< the problem is here, it can't be ( -N:1:N ) or ( -N:N ) cn = 2/(1j*n*wo); y = y + A*real(cn*exp(1j*n*wo*t)); end cla; P = T0/2; plot([-5 -4 -4 -3 -3 -2 -2 -1 -1 0 0 1 1 2 2 3 3 4 4 5],... [-A -A A A -A -A A A -A -A A A -A -A A A -A -A A A], ':'); hold; plot(t,y); xlabel('t (seconds)'); ylabel('y(t)'); ttle = ['Exponential Fourier Series with N = ',... num2str(N)]; title(ttle); hold; pause(0.5); end