[R] Stuck with FFT

Rthoughts seb.brockel at northampton.ac.uk
Mon Oct 27 19:01:57 CET 2008

Dear all,

Before I can get into serious Fourier analysis of Radon time-series I am
practising with 24hour and 24.8hour sinusoids to assist with my
interpretation of signals ittributed to tidal input to Radon time series.

I am stuck. I have tried researching this to no avail. I am awating a book
that should describe fourier transforms in detail and another one that
should discuss the R application.

I know what the command line is but I can't get it to refer to the array.

What is 'z'? If I have a table open entitled '24hsinusoids' with date/ time
column by the hour from January 01 2008 00:00 to January 02 2011  00:00
(X01.06.2008) (time column listed as X00:00) with corresponding sinudoidal
signal value column (X100) to give a complete curve for 24hours spread as
curves over the whole time-span, how can I fft from this table?

fft(z, inverse = FALSE) gives me as; object 'z' not found.

Please help and explain how R recognises the table and does fft's from it.
The time-series is discrete and periodic (or should be, as I need to analyse
my Radon time-series fro exactly this and I am very stuck now).

Thank you with all my heart if you can help.
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