On 04/09/2008 4:44 PM, Oliver Bandel wrote:
Zitat von Duncan Murdoch <[EMAIL PROTECTED]>:
Oliver Bandel wrote:
Hello,
I'm new to R (using it since about two weeks),
but absolutely a fan of it from the beginning on. :-)
Best tool for working with data I found. :-)
I tried using the fft() and other funcitons for
analysing time series.
What I would be glad to have, would be a
convenient way to display the complex result
of a fft in a way, that real and imaginary parts
each use an axis for themselves, and the index of the
resulting values use the third axe.
When displaying this as a 3D->2D picture,
it also would be nice, to change the view,
like it can be done with persp().
Is there already a package or script for preparing the data
of an fft to be displayed in this way?
I don't find this very enlightening, but here you go:
x <- rnorm(1000)
f <- fft(x)
library(rgl)
plot3d(1:length(f), Re(f), Im(f))
[...]
Ok, this is a starting point. :-)
It would be enlightening, if you have a timeseries that is not
noise only, and if the plot would not use dots.
So, using a timeseries that is derived from some data
could be very interesting. But rnorm creates noise only,
and not a deterministic signal. So the resulting fft values
look quite boring ;-)
Instead of dots, a line from the index-axis at Re=0, Im=0
to the value of the fft at that index should be drawn.
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. Alternatively, play3d(spin3d())
will spin it, or par3d(userMatrix=rotationMatrix(...)) for a fixed setting.
Duncan Murdoch
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