[Tutor] fourier transform

[Danny Yoo]

On Fri, 29 Jul 2005, Jeff Peery wrote:

> Hello, I have a signal that I want to do a fourier transform on. I tried
> using FFT.fft(data).real but I don't understand the output.  what is
> output from this function, and why doesn't it require amplitude and time
> as inputs?

Hi Jeff,

Do you mean the fast fourier transform stuff in the third-party Numarray
package?

    http://www.esrf.fr/computing/bliss/python2/NumArray/html/node50.html

According to the documentation, it's returning a list of the complex
coefficients of the transform.  According to Wikipedia, all the
tranformation needs in a sequence of n complex numbers, and returns a list
of complex numbers.

    http://en.wikipedia.org/wiki/Fourier_transform

By default, numarray.fft will return 'n' complex numbers, but it can take
in an optional argument 'n'.  The transform doesn't need to know about
amplitude or time.


My background in this is actually very very weak, so you may want to ask
other people how to interpret the results of the FFT.  Good luck to you!