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In this note, analysis of time delay systems using Lambert W function approach is reassessed. A common canonical form of time delay systems is defined. We extended the recent results of [6] for second order into nth order system. The…

Systems and Control · Computer Science 2017-09-05 Niraj Choudhary , Janardhanan Sivaramakrishnan , Indra Narayan Kar

The full width at half maximum (FWHM) is a useful quantity for characterizing the bandwidth of unimodal functions. However, a closed-form expression for the FWHM of gamma-shaped functions-i.e. functions that are shaped like the gamma…

Signal Processing · Electrical Eng. & Systems 2025-09-25 Anthony LoPrete , Johannes Burge

In this work, we develop a method for rational approximation of the Fourier transform (FT) based on the real and imaginary parts of the complex error function \[ w(z) = e^{-z^2}(1 - {\rm{erf}}(-iz)) = K(x,y) + iL(x,y), \qquad z = x + iy, \]…

General Mathematics · Mathematics 2025-06-25 Sanjar M. Abrarov , Rehan Siddiqui , Rajinder K. Jagpal , Brendan M. Quine

In this paper we present two efficient approximations for the complex error function $w \left( {z} \right)$ with small imaginary argument $\operatorname{Im}{\left[ { z } \right]} < < 1$ over the range $0 \le \operatorname{Re}{\left[ { z }…

Numerical Analysis · Mathematics 2015-04-13 S. M. Abrarov , B. M. Quine

Numerically obtaining the inverse of a function is a common task for many scientific problems, often solved using a Newton iteration method. Here we describe an alternative scheme, based on switching variables followed by spline…

Computational Physics · Physics 2020-03-09 Daniele Tommasini , David N. Olivieri

We present a new method for approximating real-valued functions on ${\mathbb R}^+$ by linear combinations of exponential functions with complex coefficients. The approach is based on a multi-point Pad\'e approximation of the Laplace…

Numerical Analysis · Mathematics 2026-05-05 Alexey Kuznetsov , Armin Mohammadioroojeh

We investigate solutions to the functional equation $f(f(x)) = e^x$, which can be interpreted as the problem of finding a half iterate of the exponential map. While no elementary solution exists, we construct and analyze non-elementary…

Numerical Analysis · Mathematics 2025-09-30 Sanay Nesargi , Gregory Roudenko

Our paper introduces a novel method for calculating the inverse $\mathcal{Z}$-transform of rational functions. Unlike some existing approaches that rely on partial fraction expansion and involve dividing by $z$, our method allows for the…

Optimization and Control · Mathematics 2024-06-11 MohammadJavad Vaez , Alireza Hosseini , Kamal Jamshidi

Originating from a system theory and an input/output point of view, I introduce a new class of generalized distributions. A parametric nonlinear transformation converts a random variable $X$ into a so-called Lambert $W$ random variable $Y$,…

Applications · Statistics 2015-03-13 Georg M. Goerg

The Lambert $W$ function, giving the solutions of a simple transcendental equation, has become a famous function and arises in many applications in combinatorics, physics, or population dyamics just to mention a few. In the last decade it…

Classical Analysis and ODEs · Mathematics 2015-06-23 István Mező , Árpád Baricz

In this paper, several modifications are introduced to the functional approximation method iterLap to reduce the approximation error, including stopping rule adjustment, proposal of new residual function, starting point selection for…

Methodology · Statistics 2015-09-23 Tiep Mai , Simon Wilson

The Lambert W function was introduced by Euler in 1779, but was not well-known until it was implemented in Maple, and the seminal paper of Corless, Gonnet, Hare, Jeffrey and Khuth was published in 1996. In this note we describe a simple…

Classical Analysis and ODEs · Mathematics 2017-03-21 Alexander Kheyfits

In this paper, we study the Lambert-Tsallis function, which is a generalization of the Lambert function with two real parameters. We give a condition on the parameters such that there exists a complex domain touching zero on boundary which…

Complex Variables · Mathematics 2020-11-13 Hideto Nakashima , Piotr Graczyk

In this paper, we present an overview of the recent developments of functional quantization of stochastic processes, with an emphasis on the quadratic case. Functional quantization is a way to approximate a process, viewed as a…

Probability · Mathematics 2013-04-03 Gilles Pagès

We present a new simple algorithm for efficient, and relatively accurate computation of the Faddeyeva function w(z). The algorithm carefully exploits previous approximations by Hui et al [1978] and Humlicek [1982] along with asymptotic…

Instrumentation and Methods for Astrophysics · Physics 2017-11-16 Mofreh R. Zaghloul

We present a new rational approximation algorithm based on the empirical interpolation method for interpolating a family of parametrized functions to rational polynomials with invariant poles, leading to efficient numerical algorithms for…

Numerical Analysis · Mathematics 2025-01-23 Aidi Li , Yuwen Li

In this paper we introduce the $p$-adic analogue of the Lambert $W$ function, and study its main properties.

Classical Analysis and ODEs · Mathematics 2018-01-03 István Mező

In this work, we propose an extensive numerical study on approximating the absolute value function. The methods presented in this paper compute approximants in the form of rational functions and have been proposed relatively recently, e.g.,…

Numerical Analysis · Mathematics 2020-05-07 Ion Victor Gosea , Athanasios C. Antoulas

In this article, we deal with the efficient computation of the Wright function in the cases of interest for the expression of solutions of some fractional differential equations. The proposed algorithm is based on the inversion of the…

Numerical Analysis · Mathematics 2024-09-16 Lidia Aceto , Fabio Durastante

Problems formulated in terms of logarithmic or exponential equations often use the Lambert $W$ function in their solutions. Expansions, approximations and bounds on $W$ have been derived in an effort to gain a better understanding of the…

Information Theory · Computer Science 2016-01-20 Ioannis Chatzigeorgiou