Re: graphing frequency & amplitude?
- To: mathgroup at smc.vnet.net
- Subject: [mg79209] Re: [mg79153] graphing frequency & amplitude?
- From: DrMajorBob <drmajorbob at bigfoot.com>
- Date: Sat, 21 Jul 2007 04:24:09 -0400 (EDT)
- References: <21958580.1184920759674.JavaMail.root@m35>
- Reply-to: drmajorbob at bigfoot.com
ListPlot's x-scale, as you're using it, is the numbers 1 to n, where n =
101 is the length of "data". If you want a different scale, you need to
construct it. For instance,
data = Table[10*Sin[200 t] + 10*Sin[100 t], {t, 0, 100}];
absF = Abs@Fourier@data;
The corresponding frequencies (per cycle) are
frequencies = Range[0, 100]/101;
ListPlot[Transpose@{frequencies, absF}, Joined -> True,
PlotRange -> All]
Bobby
On Fri, 20 Jul 2007 02:16:20 -0500, <efifer at fas.harvard.edu> wrote:
> Hi,
>
> I am trying to create a graph that graphs frequency versus amplitude of
> a sound
> made by the sum of two sine waves. I tried fourier transforming them and
> graphing it, yet it looks to me like the graph is plotting time rather
> than
> frequency. How do I change this?
>
> Plot[10*Sin[200t] + 10*Sin[100t], {t, 0, 1}]
>
> data = Table[10*Sin[200t] + 10*Sin[100t], {t, 0, 100}]
>
> ListPlot[Abs[Fourier[data]], PlotJoined -> True, PlotRange -> All]
>
> Thank you for the help!
> Emily
>
>
>
--
DrMajorBob at bigfoot.com