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Re: Need some help -- plot fast fourier transform

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Am 22.11.2015 um 04:13 schrieb dakupoto@gmail.com:
> On Saturday, November 21, 2015 at 5:43:09 AM UTC-5, Karl-Friedrich Ratzsch wrote:
>> Am 21.11.2015 um 05:56 schrieb dakupoto@gmail.com:
>>> Could some Gnuplot guru please provide any simple
>>> example script for plotting FFT(fast fourier
>>> transform). Currently I am just able to create
>>> scatter plots of FFT output, but I would much
>>> rather have the simple line graphs. All hints/
>>> suggestions would be greatly appreciated - thans
>>> in advance for your help.
>>
>> This doesn't explain your problem, just the direction from where it
>> landed on your feet.
>>
>> I'd say you don't want a guru, you want a nanny. Sorry.
>
> The problem is self-explanatory.
> I have generated a set of Fast
> Fourier Transform values(amplitude,
> phase) using a simple C language
> program, and the implementation is
> based on the steps described in
> Numerical Recipes in C. The C
> language program is compiled with
> GCC, running on a Fedora 18 machine.
> If I start gnuplot, and use use
> the command line
> plot 'testout' using 1:2 with lines;
> I get a beautiful symmetrical flower
> like pattern in the plot window NOT
> the set of symmetrical spikes
> associated with a spectrum.
> I have used Gnuplot for years, with
> no complaints. I tried other commamds
> as:
> plot 'testout' using 1:2 pt 5 ps 7
> and now I get a set of symmetrical
> little squares in the plot window,
> where each square represents the
> peak of each spike, but I DO NOT
> see the spikes. So, obviously
> there must be some other commands
> that I need to use, which I do not
> know. May I know what these other
> commands are ?
> I am sure I have explained the problem
> clearly. I expect  meaningful response.
>
>

When reading about the flower like plot my first suspicion was that your 
data file may probably not contain sorted data. A line plot will then 
show such funny figures, a point plot of the same data set would not 
reveal unsorted data. I have used NRC's FFT algorithms myself many years 
ago and I vaguely remember that the data returned by the functions had 
to be sorted manually.

Gnuplot plots data as presented in the data files unchanged unless you 
tell gnuplot to do so. That is why I would check the contents of the 
data file first.

Hope this helps,
Thomas

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Need some help -- plot fast fourier transform dakupoto@gmail.com - 2015-11-20 20:56 -0800
  Re: Need some help -- plot fast fourier transform Karl-Friedrich Ratzsch <mail.kfr@gmx.net> - 2015-11-21 11:43 +0100
    Re: Need some help -- plot fast fourier transform dakupoto@gmail.com - 2015-11-21 19:13 -0800
      Re: Need some help -- plot fast fourier transform Richard Owlett <rowlett@cloud85.net> - 2015-11-22 04:58 -0600
      Re: Need some help -- plot fast fourier transform Thomas Wagner <thomas.wagner.marl@freenet.de> - 2015-11-25 00:51 +0100
      Re: Need some help -- plot fast fourier transform Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2015-11-25 01:25 +0100
      Re: Need some help -- plot fast fourier transform drmcnelson@gmail.com - 2017-01-28 17:47 -0800
        Re: Need some help -- plot fast fourier transform John Edwards <johned0@gmail.com> - 2017-01-31 04:18 -0800
  Re: Need some help -- plot fast fourier transform Richard Owlett <rowlett@cloud85.net> - 2015-11-21 10:07 -0600
  Re: Need some help -- plot fast fourier transform drmcnelson@gmail.com - 2017-01-28 17:08 -0800

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