MATLAB: Trying to plot Fourier series, but just getting a straight line?

Question

Hi, i am trying to plot the a fourier series

i have the code below but all i seem to be getting is a straight line? i cannot for the life of me see what is wrong? i should be expecting something like :-

but sll i get is

Could anyone shed any light on this issue please, the code below is run with …….FourierSq(1 , 0.25 , 6)

ie a0=1 , T=0.25 and n=6

the code is meant to plot the first 6 terms of fourier series and the resulting sum of them also on the same plot

function [t,f] = FourierSq(A0,T,n)

t = 0 : T/256 : 4*T;

nn = length(t);

f = zeros(n,nn);

s = zeros(nn);

for ii = 1:n

for j = 1:nn

f(ii) = f(ii,j) + (4*A0/(2*ii-1)*pi) * sin(2*pi*(ii-1)*t(j));

s(j) = s(j) + f(ii,j);

end

end

hold on

for ii = 1:n

plot (t,f(ii,:),'r:')

end

plot(t,s,'k-','linewidth',2)

hold off

end

Answer 1

Replace

 f(ii)  = f(ii,j) +   (4*A0/(2*ii-1)*pi)  *  sin(2*pi*(ii-1)*t(j));

with

f(ii,j)  = f(ii,j) +   4*A0/((2*ii-1)*pi)  *  sin(2*pi*(2*ii-1)*t(j)/T);