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>