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Nonequispaced fast Fourier transform
Time and frequency nonequispaced

NNFFT - Fourier transform with non equispaced data in time and frequency domain

This library of C functions computes approximations of sums of the form

$\displaystyle d_j := \sum\limits_{l=1}^{L-1} \alpha_l\, \rm {e}^{2\pi i (k_l\odot N)x_j}
\quad (j =1,\ldots,M)

with $ k_l, x_j \in [-1/2,1/2)^d$ and $ \alpha_l \in \mathbb{C}$.

The algorithms are implemented by Tobias Knopp in ./examples/nnfft Related paper are

o Keiner, J., Kunis, S., and Potts, D.
Using NFFT 3 - a software library for various nonequispaced fast Fourier transforms
ACM Trans. Math. Software, accepted, (full paper ps, pdf)   2009

oPotts, D., Steidl G., and Tasche M.
Fast Fourier transforms for nonequispaced data: A tutorial.
in: Modern Sampling Theory: Mathematics and Applications, J.J. Benedetto and P. Ferreira (Eds.), Chapter 12, pages 249-274. (full paper ps.Z, pdf),   1998