FFT problems

[Roberto Hernandez]

Here I am again with a question about FFT. I posted a couple of days ago and 
got a couple of answers but apparently my question wasn't clear. I suppose 
this example should make it so.

Say I run the following:

octave:1> a = 1:17;
octave:2> fft(a)
ans =
 
 Columns 1 through 3:
 
   153.0000 +   0.0000i    -8.5000 +  45.4710i    -8.5000 +  21.9410i
 
 Columns 4 through 6:
 
    -8.5000 +  13.7280i    -8.5000 +   9.3241i    -8.5000 +   6.4189i
 
 Columns 7 through 9:
 
    -8.5000 +   4.2325i    -8.5000 +   2.4185i    -8.5000 +   0.7876i
 
 Columns 10 through 12:
 
    -8.5000 -   0.7876i    -8.5000 -   2.4185i    -8.5000 -   4.2325i
 
 Columns 13 through 15:
 
    -8.5000 -   6.4189i    -8.5000 -   9.3241i    -8.5000 -  13.7280i
 
 Columns 16 and 17:
 
    -8.5000 -  21.9410i    -8.5000 -  45.4710i

The sequence a is non-radix 2. So what algorithm did the fft() function use? 
Is it the DFT: X(k) = sum(1, N) x(i) * exp(-j*(i-i)*(k - 1)*2*pi / N) ?
Does anyone know?

Thanks,

- Roberto



-------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
Subscription information:  http://www.octave.org/archive.html
-------------------------------------------------------------