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From: platt@emory.uucp (Dan Platt)
Newsgroups: comp.lang.c
Subject: Re: fast fourier transform
Message-ID: <2176@emory.uucp>
Date: Thu, 16-Jul-87 19:06:50 EDT
Article-I.D.: emory.2176
Posted: Thu Jul 16 19:06:50 1987
Date-Received: Sat, 18-Jul-87 08:57:25 EDT
References: <1065@bloom-beacon.MIT.EDU> <3251@cit-vax.Caltech.Edu>
Reply-To: platt@emory.UUCP (Dan Platt)
Distribution: world
Organization: Math & Computer Science, Emory University, Atlanta
Lines: 14
Keywords: fft, general radix, C

In article <3251@cit-vax.Caltech.Edu> alee@tybalt.caltech.edu.UUCP (Andrew Lee) writes:
>...  What's wrong with simply padding the array with zeroes
>to a power of 2?
>
The problem with padding with zero's is that it introduces a window in the
data which the transform tries to fit with a superposition of frequencies
producing a pattern which would be the convolution of your data with a
sin(omega*T)/(omega*T) like function, where omega is the frequency, and
T is the size of the window.  This generaly produces ringing (false
oscilations) which wouldn't be inherent in your data at the start.

Hope this is  a help...
Dan