Symbolic DFFT in MATLAB?

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Palinkas Geza
Palinkas Geza 2014-3-17
评论： Christopher Creutzig 2021-8-24
Hi Guys!
I'd like to ask for your help to execute symbolic discrete FFT on a 1D array containing integers (eg. [1 1]), then plotting its abs on a continuous interval. Is it even possible with the symbolic toolbox?
Thanks in advance, Ben0it8
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Walter Roberson
Walter Roberson 2014-3-17
To check, you are only working with numeric values, but you want the result to be (e.g.) sin(42+cosh(19)) instead of the numeric equivalent ?

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回答（1 个）

Christopher Creutzig
编辑：Christopher Creutzig 2014-3-31
I have no idea what “plotting its abs on a continuous interval” means, but you certainly can get a symbolic, exact, FFT from the Symbolic Math Toolbox:
>> feval(symengine, 'numeric::fft', [1 1], 'Symbolic').'
ans =
2
0
>> feval(symengine, 'numeric::fft', [1 1 2], 'Symbolic').'
ans =
4
1/2 + 2*((3^(1/2)*i)/2 + 1/2)^2 - (3^(1/2)*i)/2
- 3^(1/2)*i + ((3^(1/2)*i)/2 + 1/2)^2
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Christopher Creutzig
Christopher Creutzig 2021-8-24
Since somebody asked (please do use the questions feature here, instead of sending me email): There is no 'numeric:ifft', but you can use 'numeric::invfft'.
Note, however, that like anything involving feval(symengine, ..., this is considered an undocumented feature and can go away at any time. If this is functionality you regard useful and important for what you do, please do reach out to support@mathworks.com and let us know that you request “proper” support in the toolbox.

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