What is the correct code for plotting an amplitude spectrum in MATLAB?

[magnifik]

i am trying to plot the amplitude spectrum for a function which has the following properties:

f(t) = 1, 0 < t < 10
f(t) = 0, 10 < t < 20
the period of the function is 20

i found the Fourier coefficients to be Fn = -(1/n*pi)(cos(n*pi) - 1)

i tried to use the following code to plot the amplitude spectrum in MATLAB:
% up to the 10th harmonic
n = 10;
for n = -N:2:N,
cn = (-cos(n*pi)+1)/(n*pi); % Fourier coefficient
stem(n, abs(cn))
end

however, this plots a straight line with a circle at 10. I'm not sure how to fix this as i am a MATLAB newbie

 

[Valkarie]

! any help would be appreciated!If this is not the correct code to plot an amplitude spectrum, could someone please provide the correct code?The code you provided is for plotting the Fourier coefficients of the signal. To plot the amplitude spectrum, you need to use the following code:% up to the 10th harmonicN = 10;for n = -N:2:N,cn = (-cos(n*pi)+1)/(n*pi); % Fourier coefficientAmp(n+N+1) = abs(cn);endstem(-N:2:N, Amp)