Help with Fourier transform fft

I need to use the matlab function 'fft' to perform a Fourier transform, but the problem is that it always gives me a double-sided signal, while I would like to have a one-side signal. I sometimes use this function :

function four=FourierDir(t,s,nu)

% number of points in the time domain
N=length(t);
Nf=length(nu);

% sampling step in the time domain
Dt=diff(t);
Dt(N)=Dt(N-1);

four=zeros(1,Nf);

for ii=1:Nf

      four(ii)=sum(Dt.*s.*exp(-1i*2*pi.*t.*nu(ii)));

end;

Can you suggest me an equivalent one made with fft , given as input t, s and nu ? Thanks so much.

[Mikhail]

Please explain, what do you mean by double-sided signal and one-side signal

[Rick Rosson]

The Discrete Fourier Transform of a real-valued signal is conjugate symmetric. The double-sided spectrum shows the spectrum as a function of both positive and negative frequencies on the range [-Fs/2,+Fs/2), whereas the single-sided spectrum shows the spectrum for positive frequencies only, on [0,+Fs/2).

Answer 1

[Rick Rosson]

function [ X,f,t ] = mydft(x,Fs)

     % Assumes x is an N x 1 column vector
     % and Fs is the sampling rate.

     N = size(x,1);
     dt = 1/Fs;
     t = dt*(0:N-1)';

     dF = Fs/N;
     f = dF*(0:N/2-1)';

     X = fft(x)/N;
     X = X(1:N/2);
     X(2:end) = 2*X(2:end);

     figure;
     plot(f,abs(X));

end

Answer 2

[Youssef Khmou]

Generally fft is two sided , you just need to truncate it :

     F=f(1:floor(end/2));

Answer 3

[Shravankumar P]

have a look at this

http://www.mathworks.in/help/matlab/ref/fft.html