Hi Alle Meije Wink,
yes, both basis sets refer to a windowed Fourier transform set. The
difference lies in the shape of the window: The 'Fourier set' uses a
rectangular window, whereas the 'Windowed Fourier set' (SPM99) or the
'Fourier Set (Hanning)' (SPM2) use a Hanning window.
The weights of the window are important when it comes to estimating the
spectrum of a truncated signal. This is discussed in signal processing
books, e.g. the classic Oppenheim+ Schafer, discrete-time signal
processing. Or if you want something more in the time-series literature:
A.C Harvey, Time Series Models.
The order parameter refers to the number of generated regressors. SPM
steps through the frequencies, starting at 1, up to your order parameter
and generates two regressors per order step, one sine and one cosine.
Note that SPM orthogonalizes the resulting matrix, which has the effect
that there are no redundant regressors in your set.
Stefan
Alle Meije Wink wrote:
>Dear SPM'ers
>
>Does anybody know a good reference on what the difference is between the
>fourier basis set and the windowed fourier basis set (I assume both
>basis sets only span the peristimulus window)? Also, some help on the
>'order' parameter would be very helpful.
>
>Regards
>Alle Meije Wink
>
>--
>
> Alle Meije Wink
>
> Institute for Mathematics and Computing Science
> University of Groningen
>
> P.O. Box 800 9700 AV Groningen
> Telephone: +31 50 363 71 27 Fax: +31 50 363 38 00
> E-mail: [log in to unmask] WWW: http://www.cs.rug.nl/~wink
>
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> (see http://www.fsf.org/philosophy/no-word-attachments.html)
>
>
>
>
--
Dr. Stefan Kiebel
Wellcome Dept of Imaging Neuroscience
Institute of Neurology, UCL
12 Queen Square
London WC1N 3BG
Phone: (+44) 20 7833 7478
Fax: (+44) 20 7813 1420
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