What is the Fourier Function of Matlab doing?

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Niklas Kurz
Niklas Kurz 2021-1-15
评论： Paul 2025-3-30
Hidden in the Matlab basic functions I discovered
fourier(f)
existst. This seems useful I thought, because It applies the fourier-transform to the function f by calculating the complex integral.
But how can I take use of that? I thought, by doing the transform, I can simply plot it:
syms x
FT = fourier(x^2)
fplot(FT)
isn't doing much. Is there a misunderstanding at the root?

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采纳的回答

Walter Roberson
Walter Roberson 2021-1-15
Ran in:
https://math.stackexchange.com/questions/1707452/what-is-the-fourier-transform-of-fx-x2
syms x w
FT(w) = fourier(x^2, x, w)
FT(w) = 
FT(-1), FT(0), FT(1)
ans = 
0
ans = 
ans = 
0
fplot(FT)
The empty plot is to be expected as the value is 0 everywhere exact at w = 0 exactly, where it is -infinity .
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Guillermo Aldana
Guillermo Aldana 2025-3-30
There are at least 3 defintions of the Fourier Transform - Physic, math and engineering use slighlty different versions, some even with a 180 phase shift in frequency - which definition does matlab use?
Paul
Paul 2025-3-30
See the More About section of the fourier doc page for the default parameterization of the Fourier transform. See sympref for how to specify parameters that aren't the defaults.

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