[R] Plotting the complex fft in 3D?

Martin Maechler maechler at stat.math.ethz.ch
Sat Sep 6 11:07:01 CEST 2008

Just another remakr on this thread.

I you have  time series and think about its fourier transform
(EE language) then you should know that the statistical language
of that is "spectral analysis" or maybe
 "frequency domain time-series analysis"
and the R function to consider should definitely be

spectrum()  which is a wrapper (among others) to spec.pgram()
-- which calls fft() -- for computing the so-called
If you learn more about the topic, you will learn that in almost
all cases you'd consider a *smoothed* version of the
periodogram, etc etc (because the so-called *raw* periodgram is
*in*consistent as an estimate fo the underlying true spectrum).
The Time-Series chapter/section of the MASS book is very helpful
here, IIRC.

Martin Maechler, ETH Zurich

>>>>> "OB" == Oliver Bandel <oliver at first.in-berlin.de>
>>>>>     on Thu,  4 Sep 2008 23:16:07 +0200 writes:

    OB> Zitat von Duncan Murdoch <murdoch at stats.uwo.ca>:
    >> On 04/09/2008 4:44 PM, Oliver Bandel wrote:
    >> > Zitat von Duncan Murdoch <murdoch at stats.uwo.ca>:
    >> >
    >> >> Oliver Bandel wrote:
    >> >>> Hello,
    >> >>>
    >> >>>
    OB> [...]

    >> plot3d doesn't support that directly, but you could plot with
    >> type='n',
    >> then use segments3d to add the lines.
    >> >
    >> > BTW: how to change the perspective? I did not found an
    >> > angle-parameter for the plot3d()-function.
    >> Just grab it with your mouse and drag.

    OB> Wow, coool! :-)

    OB> Well, rgl.... I think "gl" stands for OpenGl.

    OB> Fine. :-)

    >> Alternatively,
    >> play3d(spin3d())
    >> will spin it, or par3d(userMatrix=rotationMatrix(...)) for a fixed
    >> setting.

    OB> Ok, some thinsg to play with.

    OB> Thank you.

    OB> Ciao,
    OB> Oliver

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