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Computing
Article . 1984 . Peer-reviewed
License: Springer TDM
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Eine schnelle Mellin-Transformation

Authors: Gerhard West;

Eine schnelle Mellin-Transformation

Abstract

A numerical method is developed which handles the Mellin transform (1) \(M_{\epsilon}(y;f)=\int^{\infty}_{0}x^{-iy-\epsilon}f(x)dx,y\in [0,\infty),\epsilon \geq 0,i=\sqrt{\quad -1}\) of a Fourier-bandlimited function f(x). Denoting \(F(z)(F(z)=0\) for \(z\geq Z_ 0)\) the Fourier transform of the even continuation of f(x), then instead of (1) one can take (2) \(M_{\epsilon}(y;f)=\int^{\infty}_{0}z^{iy+\epsilon - 1}F(z)dz=\int^{Z}_{0}z^{iy+\quad \epsilon -1}F(z)dz\), \(Z\geq Z_ 0\) because \(M'_{\epsilon}(y;f)=h_{\epsilon}(y)M_{\epsilon}(y;f)\) holds \((h_{\epsilon}(y)\) is a function independent on f). In view of the sampling theorem F(z) may be represented by the Fourier series \(F(z)=\Delta x\{f(0)+2\sum^{\infty}_{n=1}\cos (2\pi zn\Delta x)\) f(n\(\Delta\) x)\(\}\) provided that \(\Delta\) \(x\leq 1/(2Z)\). Substituting this into (2) we arrive at (3) \(M_{\epsilon}(y;f)=\sum^{\infty}_{n=0}\psi_{\epsilon,n}(y)f(n\Delta x)\) [\textit{M. H. Brill} and the author, Elektron. Informationsverarbeitung Kybernetik 20, 229-233 (1984; Zbl 0557.65085)]. The author suggests a modification of the Mellin kernel \(z^{iy+\epsilon -1}\) in the interval \((Z_ 0,Z]\) to improve convergence properties of (3). Moreover, the convergence may be controlled because it becomes faster with growing \(\epsilon\) and Z (or sampling frequency). Numerical examples are included which illustrate that 50 to 100 terms of (3) are sufficient if \(\epsilon =2\) and \(Z=2Z_ 0\). The required \(\psi_{\epsilon,n}\) are independent on f and may be precomputed within a machine precision. The presented method may enhance the utility of the Mellin transform in scale-invariant pattern recognition.

Keywords

sampling theorem, convergence, Trigonometric approximation, Numerical examples, Pattern recognition, speech recognition, pattern recognition, Numerical methods for trigonometric approximation and interpolation, Fourier series, Fourier transform, Fourier-bandlimited function, Special integral transforms (Legendre, Hilbert, etc.), Numerical methods for integral transforms, Mellin transform

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citations
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
1
Average
Average
Average
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