Hi, All

I have original mass spectrom which is time domain signal. Then I use fft

in Matlab to fourier transform into powerspectrum. Code as below:

a=textread(C:\notebook\070111.txt')

%load data into a single column matrix called "a"

At(a,65536); %built in m file, fft of matrix a for 2^16 element.

Pa=A.*conj(A)/65536; %calculate the intensity of A

f = (0:32768)/65536; % create the frequency of x-axis

h=ones(1,32769); %create a vector of 1

g=h./f; %the frequency of x-axis

m=g/16;%factor the number of sample points.

plot(m,Pa(1:32769));

Now I have question on how to perform inverse FFT for just part of the

result of FFT in the region of (200:5000)? And how to calculate the x

axis?

Thanks for advance.

Bella