Discover MakerZone

MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi

Learn more

Discover what MATLAB® can do for your career.

Opportunities for recent engineering grads.

Apply Today

Thread Subject:
Why does the default fft data number change for a identification data

Subject: Why does the default fft data number change for a identification data

From: fl

Date: 4 Apr, 2013 16:46:14

Message: 1 of 2

Hi,

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
get(fdata)

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?

Thanks,

Subject: Why does the default fft data number change for a

From: Polly Onymy

Date: 4 Apr, 2013 19:11:17

Message: 2 of 2

On Thu, 04 Apr 2013 09:46:14 -0700, fl wrote:
 
> 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 get(fdata)
>
> 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?

What did you notice about workspace arrays when you copied, pasted, and ran one of the example programs in the
section "Help -> Matlab -> Mathematics -> Fourier Analysis and Filtering"?

> Thanks,

for what?

Tags for this Thread

No tags are associated with this thread.

What are tags?

A tag is like a keyword or category label associated with each thread. Tags make it easier for you to find threads of interest.

Anyone can tag a thread. Tags are public and visible to everyone.

Contact us