Date: Apr 4, 2013 12:46 PM
Author: fl
Subject: Why does the default fft data number change for a identification data


I try to run a snippnet of identification toolbox user guide:

% Load input u2 and output y2
load dryer2;
% Create iddata object
tdata = iddata(y2,u2,0.08);
% Take the Fourier transform of the data
% transforming it to frequency domain
fdata = fft(tdata)
% Get property values of data

The length of tdata is 1000 while the length of fdata is 501. I have check function fft and I do not find anything can explain it to me. Could you help me on this question?