[R] fft question

[Martin Maechler]

>>>>> "Frank" == Frank Gerrit Zoellner <fzoellne at TechFak.Uni-Bielefeld.DE>
>>>>>     on Thu, 11 Mar 2004 16:04:27 +0100 writes:

    Frank> Hi!  I am using the fft() function the base package
    Frank> to transform some 1d signal.  If I use this standar
    Frank> fucntion I get a very huge first fourier coeficient.
    Frank> I think this dues to the handling of the borders of
    Frank> the signal.  Usually in fft especially in image
    Frank> processing the signal is simulated to be continuous
    Frank> by adding the signal several times periodically. My
    Frank> question is, is there some function implemented in R
    Frank> handling this or do I have to combine my data
    Frank> manually ?

Yes, manually, like

  fx <- fft(rep(x, 4))

when you want to quadruple your signal.
Martin