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Discrete Fourier Transform for dataset (on Wolfram|Alpha)

Posted 10 years ago

Sorry if my question is a duplicate of Trying To Obtain Fourier Cosine Coeficients of A Set of data But I did not find a decent solution there. I'm trying to find Discrete Fourier transform on my set of data (attached as diff.txt file). I've tried queries: "Fourier decomposition" and "FourierDCT". "FourierDCT" should work, but it says, 'Assuming "FourierDCT" is referring to a Wolfram Language function | Use as a math function instead' (fourier_dct.png). When I go to link under words "math function" I get fourier_dct_math_function.png.

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POSTED BY: Andrew Kravtsun
3 Replies
Posted 10 years ago

I guess u're writing your request in wrong form. Try something like this

FourierDCT[diff]

I downloaded your file and ran it in Mathematica. This is what i have as a result: enter image description here

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POSTED BY: Ilya Pekert
Posted 10 years ago

Thanks for your reply, Ilya! I kind of know, that I am writing my request in a wrong form. I just want to know how to write it right. First of all, unfortunately, I don't have Mathematica, my question is about Wolfram Alpha only.

Second, I already tried what you suggested - please see my attached screenshot for details. Downloaded file is called "c.txt".

Third, I failed to watch your file "FourierDCT.nb" in my CDF player (version 9.0.2.0). Error message is, FourierDCT::fftl: "Argument \!(\"-1.000000000000000000e+00 0.000000000000000000e+00\\n-9.949874686716791983e-01 0.000000000000000000e+00\\n-9.899749373433583965e-01 0.000000000\" [Ellipsis] \"3433581745e-01 2.958823122697410227e-02\\n9.949874686716790873e-01 2.215147684345047940e-02\\n1.000000000000000000e+00 1.559357775423273439e-02\") is not a non-empty list or rectangular array of numeric quantities."

Could you please save it in some sort of compatibility mode?

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POSTED BY: Andrew Kravtsun
Posted 10 years ago

I guess the data in file diff.txt is not in a proper format. I'm not that acknowledged in this spehre of math, you know. But Mathematica keeps giving me the same error reply:

FourierDCT::fftl (then it's listing arguments from file) is not a non-empty list or rectangular array of numeric quantities.

If u haven't tried, u can read this article for help Discrete Fourier Transforms

P.S I've tried running an example and it works perfect enter image description here

Hope I've helped you a little bit. And if u solve your problem, I'll be glad to know the answer :)

POSTED BY: Ilya Pekert
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