Re: Fourier Transform Spectroscopy w/ Mathematica
- To: mathgroup at smc.vnet.net
- Subject: [mg46771] Re: [mg46744] Fourier Transform Spectroscopy w/ Mathematica
- From: Yasvir Tesiram <yat at omrf.ouhsc.edu>
- Date: Sun, 7 Mar 2004 01:33:51 -0500 (EST)
- References: <200403050646.BAA05045@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
G'day,
Stuff like this maybe?
I haven't related the number of points in x to the frequency or
anything and I leave that up to you. Sampling schemes differ between
disciplines and can mean very different things in reality.
Some decaying sinusoid.
fid1 = Table[Cos[20.0t] Exp[-0.10t], {t, 0.0, 10, 0.1}];
l1 = Length[fid1];
ListPlot[fid1, PlotJoined -> True]
Here is the Fourier transform without zero-filling.
ft1 = Fourier[fid1];
left = Take[Re[ft1], (l1 - 1)/2];
right = Take[Im[ft1], (l1 - 1)/2];
(*a phasing step *)
p[a_, b_, im_, re_] := Table[Sin[a + im]] + Table[Cos[b + re]]
ListPlot[p[0, 3.52, left, right], PlotRange -> All, PlotJoined -> True]
Here is the Fourier transform with zero filling. I suppose you now need
a window function having truncated the data somewhat.
fid2 = PadRight[fid1, 256];
l2 = Length[fid2];
ListPlot[fid2, PlotJoined -> True, PlotRange -> All]
ft2 = Fourier[fid2];
left1 = Take[Re[ft2], (l2)/2];
right1 = Take[Im[ft2], (l2)/2];
p[a_, b_, im_, re_] := Table[Sin[a + im]] + Table[Cos[b + re]]
ListPlot[p[0, 3.14, left1, right1], PlotRange -> All, PlotJoined ->
True, Frame -> True]
Yas
On Mar 5, 2004, at 12:46 AM, Kevin Gross wrote:
> Does anybody have an example notebook for transforming interferograms
> into spectra via FFT?
>
> Thanks,
>
> Kevin
>
- References:
- Fourier Transform Spectroscopy w/ Mathematica
- From: Kevin Gross <kc144@woh.rr.com>
- Fourier Transform Spectroscopy w/ Mathematica