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Re: Discrete Fourier Transform


Catherine,

Fourier[x] gives you N=Length[x] Fourier coefficients. The resoution is 1/N Hz or 2 Pi/N radians per second (assuming, of course, that the samples of the time series x are spaced 1 second apart). To change the resolution pad the sequence with zeros:

Fourier[PadRight[x, M]]

For more details consult any modern undergraduate EE textbook on signals and systems, such as Oppenheim, or Haykin, or Carlson.

Mariusz  



>>Hello everyone,
>>
>>I am attempting to perform a discrete Fourier transform on a time series
>>using Mathematica 4.0.  (I'd like to determine the period of the signal.)
>>Unfortunately, I noticed that I cannot control the frequency resolution of
>>this transform.  I also have no idea what units the frequency is in.
>>
>>Do you know of any way to get around the problem?
>>
>>Thanks so much.
>>
>>Catherine Neish




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