[R] Preparing timestamped data for fourier analysis

[Milos Zarkovic]

I believe that FFT is not appropriate. However Lomb-Scargle periodogram 
could be used.

Sincerely

Milos Zarkovic

******************************************************
Milos Zarkovic MD, Ph.D.
Associate Professor of Internal Medicine
Institute of Endocrinology
Dr Subotica 13
11000 Beograd
Serbia

Tel +381-63-202-925
Fax +381-11-685-357

Email mzarkov at eunet.yu
******************************************************


----- Original Message ----- 
From: "Pete Cap" <peteoutside at yahoo.com>
To: <r-help at stat.math.ethz.ch>
Sent: Monday, June 13, 2005 7:16 PM
Subject: [R] Preparing timestamped data for fourier analysis


> Greetings all,
>
> I'm working on a project trying to apply fourier analysis to timestamped 
> router logs, using R to perform the analysis.  The idea is to determine if 
> any type of traffic (say, outgoing ICMP requests) has strong periodic 
> features because it may indicate a compromise somewhere on the network.
>
> The FFT requires all data points to be evenly spaced, but the recorded 
> events do not occur at a consistent constant dt, so I need to "zero pad" 
> the data.  I can do this for small data sets (say, one day's worth of 
> traffic) in excel.
>
> However, I am now attempting it on a large scale using a 25-day router 
> log, which should have 2,160,000 records.  The log actually contains only 
> 56,725 records.
>
> So, I'm looking for ways in which to pad the data in R.  If anyone could 
> just point me at the right man pages to read that would be itself a great 
> help.
>
> Thanks in advance,
>
> Pete
>
>
> ---------------------------------
>
>
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>
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