how to plot this function
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4 Comments
Walter Roberson
on 18 May 2019
(n<-2 & n>2)
is never true. However, since you are multiplying that by 0, if it somehow did match it would contribute 0 anyhow. You can just leave out that term.
Your x axis is wrong. You are effectively using your n as your frequency, including negative n. If you are going to plot negative frequencies then you need to fftshift() . And use more points.
Read the first example of fft() to see how to properly plot.
Answers (2)
Sulaymon Eshkabilov
on 18 May 2019
n = -5:1:5;
x=1*(n>=-2 & n<=2)+0*(n<-2 & n>2);
L = length(n); Fs = 1;
Nblock = 128; % Block size
Y = fft(x, Nblock)/L;
f = Fs/2*linspace(0,5, Nblock/2+1);
plot(f, 2*abs(Y(1:Nblock/2+1)))
xlabel('frequency, [Hz]'), ylabel('Amplitude')
title('Single-sided Spectrum'), shg
3 Comments
Sulaymon Eshkabilov
on 18 May 2019
Hi,
Here is the full spectrum calculation:
n = -5:1:5;
x=1*(n>=-2 & n<=2);
L = length(n); Fs = 1;
Nblock = 128; % Block size
Y = fft(x, Nblock)/L;
f = Fs/2*linspace(0,5, Nblock);
plot(f, 2*abs(Y(1:Nblock)))
xlabel('frequency, [Hz]'), ylabel('Amplitude')
title('Single-sided Spectrum'), shg
Good luck.
4 Comments
Walter Roberson
on 19 May 2019
t = linspace(0,10);
ft = fft(t);
subplot(1,2,1); plot(abs(ft)); %what you are doing now
subplot(1,2,2); plot(abs(fftshift(ft))); %what you need to do in order to get the 0 in the center
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