How to plot FFT of sine wave?

Asked Apr 09 '17 at 20:14

Active Apr 09 '17 at 20:14

Viewed 79 times

I have problem with plot of FFT signal

y=sin(log10(16)/log(6));

Here is my code:

y=sin(log10(16)/log(6));
Y = fft(y);
fs = 100;
P2 = abs(Y/length(y));
P1 = P2(1:length(y)/2+1);
P1(2:end-1)=2*P1(2:end-1);
f=fs*(0:length(y)/2)/length(y);
bar(f,P1);
xlabel('f[HZ]');
ylabel('|P1(f)|');

When I plot this code above, Matlab return me only a blue bar...

asked Apr 09 '17 at 20:14

Szymon

2

sin(log10(16)/log(6)) does not look like a sine wave to me, that's just some constant – harold Apr 09 '17 at 20:16
Yes, but how I can plot this constant? – Szymon Apr 09 '17 at 20:18
The constant or its fourier transform? Not that either is very interesting to look at in a plot.. – harold Apr 09 '17 at 20:28
If I have sin(log10(16)/log(6)), how to make FFT of this constant? – Szymon Apr 09 '17 at 20:31
@Szymon you need to check your input data. `sin(log10(16)/log(6))` is just a single point. Its FFT is also a single point that is a blue bar on your plot. – brainkz Apr 09 '17 at 20:46
@Szymon if you need an FFT of constant, use `N=100;y=sin(log10(16)/log(6))*ones(1,N);` – brainkz Apr 09 '17 at 20:47
I use time vector such as t = (0:0.01:1)'; and plot FFT from sin(log10(16)/log(6)*t) – Szymon Apr 10 '17 at 08:25

How to plot FFT of sine wave?

0 Answers0