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4

Sjoerd's approach using SARIMAProcess and TimeSeriesModelFit, in particular the last portion with in which you test SARIMA models of differing orders and observe which models are particularly favoured by the AIC, is certainly a valid approach. However, since you asked about periodograms and other spectral methods in your question, I thought I'd give an ...


4

First, paste your two columns of data copied from Google docs in Mathematica: data = ImportString["Day\tTraffic 1/12/2014\t3 2/12/2014\t15 . . . 5/5/2015\t109 6/5/2015\t282", "TSV"] // Rest; Then convert the few 14s and 15s mingled between the 2014s and 2015s to full years, and convert to a TimeSeries: dataTS = MapAt[ ...


0

Move the dimension you want to FT to the lowest level using Transpose, FT there using Map, then Transpose back. For example, if you want to only transform the top level of a 3D array, then do this: F[h_]:=Transpose[ Map[Fourier, Transpose[h, {3, 2, 1}], {2}], {3, 2, 1}]


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There appears to be a problem with version 10.1 compared to version 10.0 Your direct integration implies that your Fourier parameters are {-1, 1} $Version "10.0 for Mac OS X x86 (64-bit) (December 4, 2014)" F[w_] = 1/(1 - I*w); f[t_] = InverseFourierTransform[F[w], w, t, FourierParameters -> {-1, 1}] (2*Pi*HeavisideTheta[t])/E^t F[w] == ...


4

The functions Fourier, FourierTransform, InverseFourier, and InverseFourierTransform (possibly others that I am not aware of) all accept a parameter called FourierParameters to determine the flavor of transform performed. By default, the value of FourierParameters is {0, 1}, which gives the results you've observed. To run a 'traditional' Fourier transform, ...


2

decibel is a relative unit. I'm pretty sure there is no implied standard reference in audio processing, (it looks like audiologists have a few go-to's e.g. dB HL, but I don't know what Audacity does). That said, you need a reference value. Since you're looking at FFT's the total power might be a good choice. Then decibels will tell you how strong a ...


0

Take your $y$ values (in a list myData) and convert them by the definition for decibels: 20 Log[10, #/Min[myData]] & /@ myData If your data is in the form of {{t1, v1}, {t2, v2}, ...} then in a simple (but inefficient) method: myData = {{3, 6}, {4, 8}, {5, 2}}; myMin = Min[myData[[All, 2]]]; fixedData = {#[[1]], 20 Log[10, #[[2]]/myMin]} & /@ ...



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