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Re: Discrete Fourier Transform (DFT) viewer and/or file format




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On Sun, Nov 12, 2017 at 07:45:13PM -0800, Dan Hitt wrote:
> I have some DFTs that i wish to inspect.  (Apparently DFT is a common
> acronym, but here i mean Discrete Fourier Transform.  And properly
> speaking it doesn't make sense to inspect a transform, but only to
> inspect transformed data, but i'm speaking colloquially.)

Uh, oh. To answer that without getting lost in Hilbert Space means
consulting my (rusty) crystal ball :-)

Now more seriously: what do you mean by "inspecting" a DFT?

A DFT is just a trick to approximate a Fourier transform on an
(approximate) function. Are you talking about one dimensional
functions (e.g. a function of time) or two (three, etc.) dimensional
functions? Their transforms are, correspondingly, one, two (and
so on) dimensional functions, so the visualization techniques
vary, depending on dimensionality and on the conventions current
in the field (engineering, social sciences, maths, whatever).

I'd recommend looking into some of the many (excellent) scientific
packages having a visualization components, each one of which
has a teeming community willing to help you.

For three examples off the top of my head (all three packaged
in Debian):

  GNU Octave   https://www.gnu.org/software/octave/
  NumPy        http://www.numpy.org/
  GNU R        https://www.r-project.org/

The last one is touted as "statistical package", but let me tell
you: all three are not only capable of visualizing (the result of)
a discrete DFT, but all three can calculate one for you :-)

Now if you are trying to visualize the result of a DFT on an image
(a special two dimensional case, where you think of the discrete
elements as of pixels), then perhaps a graphical package (e.g.
The Gimp) is your friend. Also packaged in Debian.

For more of those "scientific computing" packages, browsing this

  https://wiki.debian.org/DebianScience

might be of interest (or just drop "Debian scientific computing"
into your favourite search engine, which hopefully ain't Google).

Enjoy

- -- tomás
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