Extracting frequency from fft command

I found a post for you that asking about code for extracting particular frequency from fft,if you don't mind, i need something like that in another algorithm.

Thanks,

Answer 1

[Matt J]

For an N-point fft with time sampling interval T, the output of fftshift(fft(...)) has frequency axis (Hz) given by,

fAxis=(  (0:N-1) -ceil((N-1)/2)  )/N/T;

[saad]

sorry, but i didn't how to added to my code.

[Tewodros Abebe]

Sorry, i need to shift center frequency in 2/T. so how can i plot?