Dear all,
Simple question about the "fft" function of S-Plus (for windows):
Let`s consider a vector "ni, i=1,2,..N" (for example a vector with 2048
points). This vector is the result of sampling a analog signal at rate of "At"
(for example 1 sec).
If I perfom the a FFT, I expect to obtain another vector "Ck, k=1,2,..N/2"
(i.e. a half of length of the vector in the time domain). The frequencies
corresponding with "Ck" will be "k/(N*At)". However, with the function "fft" I
get a N-point long result.
What does it mean? Can I just ignore the second part in the follwing case?
I have a time record in the time domain, I want transform it in the frequency
domain and multiply it for a transfer function (which is a equation function of
frequency); and finally tranform the result in the time domain. Like applying a
filter!
Should I extent the filter to double or ignore the second part of the FFT
result?
Thanks in advance.
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