DFT - How to label x-axis in frequency

Hi,

I need to label my x-axis in frequency how can I do that ... follow my code

% function f2

N=length(f2);

n = 0:1:N-1; % row vector for n

k = 0:1:N-1; % row vecor for k

WN = exp(-1j*2*pi/N); % Twiddle factor (w)

nk = n'*k; % creates a N by N matrix of nk values

WNnk = WN .^ nk; % DFT matrix

Xk = (WNnk*f2 );

mag1=abs(Xk); ang1=(angle(Xk)*180)/pi;

Then here I need to plot an one sided fft Amplitude x Frequency.. Anyone can Help me???

[Orion]

Hi,

what is f2 ? it's not defined in your text, so we can't run it to try your code.

[Wellington]

Sorry

n=0:1:127;

dt2=.01;

phase=0.6108652382;

f2=sin(2*pi*4*n*dt2 + phase);

 this is the previous part of the code

Answer 1

[Orion]

your line

Xk = (WNnk*f2 );

is not working. problem of dimensions : WNnk is 128x128 matrix and f2 is a 1x128.

maybe you just want to transpose ?

Xk = (WNnk*f2' );

anyway, make sure your data are at the expected dimensions and then just plot(f2,mag1) ?

[Wellington]

Yes, I transposed f2, then the dimension is not the problem anymore.

But When I'am plotting the x-axis come up with the number between 0 and 128 and with both sides of DFT. I need one sided and frequency on x-axis

Thanks so much!!