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javaandroidalgorithmfft
slayton
slayton

Reputation: 20319

Inverse Fourier Transform in Android

Are there any Java/Android libraries that have implemented the inverse fourier transform? I've found a few that implement the fourier transform but none that implement its inverse.

Upvotes: 2

Views: 1873

Answers (1)

comingstorm
comingstorm

Reputation: 26117

A Fourier transform is almost its own inverse.

Specifically, if F[] is your Fourier transform,

F[ F[g(x)] ] = K g(-x)

(where K depends on the exact definition of your transform; see the relevant section of the wikipedia article on DFT's)

The wikipedia article suggests a number of ways to get an inverse transform. One way is to reverse the order of the input (specifically, swap x[n] with x[N-n]) before performing the transform. Another is to conjugate your data before and after you perform the transform. In any case, you will generally need to multiply by a constant factor, to recover your signal at its original amplitude.

In summary: it is quick and easy to use the regular transform to get the inverse, which is probably why they don't specifically provide one.

Upvotes: 5

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