# Thread: MATLAB Plotting Fourier series coefficients

1. ## MATLAB Plotting Fourier series coefficients

I'm trying to plot the above fourier series coefficients, what am I doing wrong? here is my matlab code:

Code:
clear
time=-1:0.01:1;
l=0.5;

x=0; %initialize to 0

for n=1:40
if (n==2*l), x=x-(1/(pi*l)); end;
if (n==(2*l+1)), x=x+(2/((pi*(2*l+1))))*(1+(2*(-1)^l)/(pi*(2*l+1))); end;
plot(time,real(x))
xlabel('time (sec)')
ylabel('x(t)')
title(['n=', int2str(n), ' Fourier Series Approximation'])
pause(1)
end

2. Originally Posted by synnexster

I'm trying to plot the above fourier series coefficients, what am I doing wrong? here is my matlab code:

Code:
clear
time=-1:0.01:1;
l=0.5;

x=0; %initialize to 0

for n=1:40
if (n==2*l), x=x-(1/(pi*l)); end;
if (n==(2*l+1))
x=x+(2/((pi*(2*l+1))))*(1+(2*(-1)^l)/(pi*(2*l+1)));
end;
plot(time,real(x))
xlabel('time (sec)')
ylabel('x(t)')
title(['n=', int2str(n), ' Fourier Series Approximation'])
pause(1)
end
1. Don't use l as a variable name, it is too easy to confuse it with 1.

2. l is a constant, so the loop only does anything when n=1, and n=2.

3. It looks as though you intend x to be an array, but its only a scalar.

4. It is not clear what you are trying to do here.

The following creates an array of the coefficients:

Code:
clear

b=zeros(1,40); %initialize to a row vector of 40 0's

for n=1:40
if (mod(n,2)==0)
L=n/2;
b(n)= -1/(pi*L);
else
L=(n+1)/2;
b(n)=2/((pi*(2*L+1))))*(1+(2*(-1)^L)/(pi*(2*L+1));
end
end
.