FFT : How to plot...

I want some help regarding the plotting of the FFT in matlab...Here is
the code :

Fs=650; %
Ts=1/Fs; %
N=2000; % number of samples wanted, vector length
%( better N=Fs; or N=Fs*2 or N=Fs/2...) why ????
Fo=1/(Ts*N) % frequency resolution
Fx=fft(x); % DFT of x
Nx=length(x); %
Fo= 1/(Ts*Nx);
f=0:Fo:Fs-Fo; % frequency vector from 0 ((N-1)/N) 2 pi = 0 Fs-Fo
plot(f(1:Nx/2),abs(Fx(1:N/2))) % we plot only the first halves of f
and Fx. 0-Fs/2
title('Frequency domain Plot of x')
xlabel('f [ Hz ]')
ylabel('Amplitude')
Now , what is this frequency resolution vector .Is there any special
mathematics in taking the frequency vector for plotting the FFT...plz
help me ...

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Your fourth line is correct, that should be your resolution equation. Now, if you want N 00 points just use fft(x,N). The signal is zero padded if length(x) < N and truncated if greater. Be careful, you're missing pi if N is odd (not your case though). To plot, just use f = [0 : N/2 - 1]*(Fs/N). Note that the last product term is your resolution (what you have).

umer_farooque78 wrote: I want some help regarding the plotting of the FFT in matlab...Here is
the code :

Fse0; %
Ts=1/Fs; %
N 00; % number of samples wanted, vector length
%( better N=Fs; or N=Fs*2 or N=Fs/2...) why ????
Fo=1/(Ts*N) % frequency resolution
Fxt(x); % DFT of x
Nx=length(x); %
Fo= 1/(Ts*Nx);
f=0:Fo:Fs-Fo; % frequency vector from 0 ((N-1)/N) 2 pi = 0 Fs-Fo
plot(f(1:Nx/2),abs(Fx(1:N/2))) % we plot only the first halves of f
and Fx. 0-Fs/2
title('Frequency domain Plot of x')
xlabel('f [ Hz ]')
ylabel('Amplitude')
Now , what is this frequency resolution vector .Is there any special
mathematics in taking the frequency vector for plotting the FFT...plz
help me ... Start a New Thread