Ljajko, Eugen

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Author's Bibliography

Parameters Estimation in Non-Negative Integer-Valued Time Series: Approach Based on Probability Generating Functions

Stojanović, Vladica; Ljajko, Eugen; Tošić, Marina

(Basel : MDPI, 2023)

TY  - JOUR
AU  - Stojanović, Vladica
AU  - Ljajko, Eugen
AU  - Tošić, Marina
PY  - 2023
UR  - https://jakov.kpu.edu.rs/handle/123456789/1645
AB  - This manuscript deals with a parameter estimation of a non-negative integer-valued (NNIV) time series based on the so-called probability generating function (PGF) method. The theoretical background of the PGF estimation technique for a very general, stationary class of NNIV time series is described, as well as the asymptotic properties of the obtained estimates. After that, a particular emphasis is given to PGF estimators of independent identical distributed (IID) and integer-valued non-negative autoregressive (INAR) series. A Monte Carlo study of the thus obtained PGF estimates, based on a numerical integration of the appropriate objective function, is also presented. For this purpose, numerical quadrature formulas were computed using Gegenbauer orthogonal polynomials. Finally, the application of the PGF estimators in the dynamic analysis of some actual data is given.
PB  - Basel : MDPI
T2  - Axioms
T1  - Parameters Estimation in Non-Negative Integer-Valued Time Series: Approach Based on Probability Generating Functions
VL  - 12
IS  - 2
SP  - 112
DO  - 10.3390/axioms12020112
ER  - 
@article{
author = "Stojanović, Vladica and Ljajko, Eugen and Tošić, Marina",
year = "2023",
abstract = "This manuscript deals with a parameter estimation of a non-negative integer-valued (NNIV) time series based on the so-called probability generating function (PGF) method. The theoretical background of the PGF estimation technique for a very general, stationary class of NNIV time series is described, as well as the asymptotic properties of the obtained estimates. After that, a particular emphasis is given to PGF estimators of independent identical distributed (IID) and integer-valued non-negative autoregressive (INAR) series. A Monte Carlo study of the thus obtained PGF estimates, based on a numerical integration of the appropriate objective function, is also presented. For this purpose, numerical quadrature formulas were computed using Gegenbauer orthogonal polynomials. Finally, the application of the PGF estimators in the dynamic analysis of some actual data is given.",
publisher = "Basel : MDPI",
journal = "Axioms",
title = "Parameters Estimation in Non-Negative Integer-Valued Time Series: Approach Based on Probability Generating Functions",
volume = "12",
number = "2",
pages = "112",
doi = "10.3390/axioms12020112"
}
Stojanović, V., Ljajko, E.,& Tošić, M.. (2023). Parameters Estimation in Non-Negative Integer-Valued Time Series: Approach Based on Probability Generating Functions. in Axioms
Basel : MDPI., 12(2), 112.
https://doi.org/10.3390/axioms12020112
Stojanović V, Ljajko E, Tošić M. Parameters Estimation in Non-Negative Integer-Valued Time Series: Approach Based on Probability Generating Functions. in Axioms. 2023;12(2):112.
doi:10.3390/axioms12020112 .
Stojanović, Vladica, Ljajko, Eugen, Tošić, Marina, "Parameters Estimation in Non-Negative Integer-Valued Time Series: Approach Based on Probability Generating Functions" in Axioms, 12, no. 2 (2023):112,
https://doi.org/10.3390/axioms12020112 . .
2

Zero-and-One Integer-Valued AR(1) Time Series with Power Series Innovations and Probability Generating Function Estimation Approach

Stojanović, Vladica S.; Bakouch, Hassan S.; Ljajko, Eugen; Qarmalah, Najla

(Basel : MDPI, 2023)

TY  - JOUR
AU  - Stojanović, Vladica S.
AU  - Bakouch, Hassan S.
AU  - Ljajko, Eugen
AU  - Qarmalah, Najla
PY  - 2023
UR  - https://jakov.kpu.edu.rs/handle/123456789/1632
AB  - Zero-and-one inflated count time series have only recently become the subject of more extensive interest and research. One of the possible approaches is represented by first-order, nonnegative, integer-valued autoregressive processes with zero-and-one inflated innovations, abbr. ZOINAR(1) processes, introduced recently, around the year 2020 to the present. This manuscript presents a generalization of ZOINAR processes, given by introducing the zero-and-one inflated power series (ZOIPS) distributions. Thus, the obtained process, named the ZOIPS-INAR(1) process, has been investigated in terms of its basic stochastic properties (e.g., moments, correlation structure and distributional properties). To estimate the parameters of the ZOIPS-INAR(1) model, in addition to the conditional least-squares (CLS) method, a recent estimation technique based on probabilitygenerating functions (PGFs) is discussed. The asymptotic properties of the obtained estimators are also examined, as well as their Monte Carlo simulation study. Finally, as an application of the ZOIPS-INAR(1) model, a dynamic analysis of the number of deaths from the disease COVID-19 in Serbia is considered.
PB  - Basel : MDPI
T2  - Mathematics
T1  - Zero-and-One Integer-Valued AR(1) Time Series with Power Series Innovations and Probability Generating Function Estimation Approach
VL  - 11
IS  - 8
SP  - 1772
DO  - 10.3390/math11081772
ER  - 
@article{
author = "Stojanović, Vladica S. and Bakouch, Hassan S. and Ljajko, Eugen and Qarmalah, Najla",
year = "2023",
abstract = "Zero-and-one inflated count time series have only recently become the subject of more extensive interest and research. One of the possible approaches is represented by first-order, nonnegative, integer-valued autoregressive processes with zero-and-one inflated innovations, abbr. ZOINAR(1) processes, introduced recently, around the year 2020 to the present. This manuscript presents a generalization of ZOINAR processes, given by introducing the zero-and-one inflated power series (ZOIPS) distributions. Thus, the obtained process, named the ZOIPS-INAR(1) process, has been investigated in terms of its basic stochastic properties (e.g., moments, correlation structure and distributional properties). To estimate the parameters of the ZOIPS-INAR(1) model, in addition to the conditional least-squares (CLS) method, a recent estimation technique based on probabilitygenerating functions (PGFs) is discussed. The asymptotic properties of the obtained estimators are also examined, as well as their Monte Carlo simulation study. Finally, as an application of the ZOIPS-INAR(1) model, a dynamic analysis of the number of deaths from the disease COVID-19 in Serbia is considered.",
publisher = "Basel : MDPI",
journal = "Mathematics",
title = "Zero-and-One Integer-Valued AR(1) Time Series with Power Series Innovations and Probability Generating Function Estimation Approach",
volume = "11",
number = "8",
pages = "1772",
doi = "10.3390/math11081772"
}
Stojanović, V. S., Bakouch, H. S., Ljajko, E.,& Qarmalah, N.. (2023). Zero-and-One Integer-Valued AR(1) Time Series with Power Series Innovations and Probability Generating Function Estimation Approach. in Mathematics
Basel : MDPI., 11(8), 1772.
https://doi.org/10.3390/math11081772
Stojanović VS, Bakouch HS, Ljajko E, Qarmalah N. Zero-and-One Integer-Valued AR(1) Time Series with Power Series Innovations and Probability Generating Function Estimation Approach. in Mathematics. 2023;11(8):1772.
doi:10.3390/math11081772 .
Stojanović, Vladica S., Bakouch, Hassan S., Ljajko, Eugen, Qarmalah, Najla, "Zero-and-One Integer-Valued AR(1) Time Series with Power Series Innovations and Probability Generating Function Estimation Approach" in Mathematics, 11, no. 8 (2023):1772,
https://doi.org/10.3390/math11081772 . .
2

The Nullity, Rank, and Invertibility of Linear Combinations of k-Potent Matrices

Tošić, Marina; Ljajko, Eugen; Kontrec, Nataša; Stojanović, Vladica

(Basel : MDPI, 2020)

TY  - JOUR
AU  - Tošić, Marina
AU  - Ljajko, Eugen
AU  - Kontrec, Nataša
AU  - Stojanović, Vladica
PY  - 2020
UR  - https://jakov.kpu.edu.rs/handle/123456789/1635
AB  - Baksalary et al. (Linear Algebra Appl., doi:10.1016/j.laa.2004.02.025, 2004) investigated the invertibility of a linear combination of idempotent matrices. This result was improved by Koliha et al. (Linear Algebra Appl., doi:10.1016/j.laa.2006.01.011, 2006) by showing that the rank of a linear combination of two idempotents is constant. In this paper, we consider similar problems for k-potent matrices. We study the rank and the nullity of a linear combination of two commuting k-potent matrices. Furthermore, the problem of the nonsingularity of linear combinations of two or three k-potent matrices is considered under some conditions. In these situations, we derive explicit formulae of their inverses.
PB  - Basel : MDPI
T2  - Mathematics
T1  - The Nullity, Rank, and Invertibility of Linear Combinations of k-Potent Matrices
VL  - 8
IS  - 12
SP  - 2147
DO  - 10.3390/math8122147
ER  - 
@article{
author = "Tošić, Marina and Ljajko, Eugen and Kontrec, Nataša and Stojanović, Vladica",
year = "2020",
abstract = "Baksalary et al. (Linear Algebra Appl., doi:10.1016/j.laa.2004.02.025, 2004) investigated the invertibility of a linear combination of idempotent matrices. This result was improved by Koliha et al. (Linear Algebra Appl., doi:10.1016/j.laa.2006.01.011, 2006) by showing that the rank of a linear combination of two idempotents is constant. In this paper, we consider similar problems for k-potent matrices. We study the rank and the nullity of a linear combination of two commuting k-potent matrices. Furthermore, the problem of the nonsingularity of linear combinations of two or three k-potent matrices is considered under some conditions. In these situations, we derive explicit formulae of their inverses.",
publisher = "Basel : MDPI",
journal = "Mathematics",
title = "The Nullity, Rank, and Invertibility of Linear Combinations of k-Potent Matrices",
volume = "8",
number = "12",
pages = "2147",
doi = "10.3390/math8122147"
}
Tošić, M., Ljajko, E., Kontrec, N.,& Stojanović, V.. (2020). The Nullity, Rank, and Invertibility of Linear Combinations of k-Potent Matrices. in Mathematics
Basel : MDPI., 8(12), 2147.
https://doi.org/10.3390/math8122147
Tošić M, Ljajko E, Kontrec N, Stojanović V. The Nullity, Rank, and Invertibility of Linear Combinations of k-Potent Matrices. in Mathematics. 2020;8(12):2147.
doi:10.3390/math8122147 .
Tošić, Marina, Ljajko, Eugen, Kontrec, Nataša, Stojanović, Vladica, "The Nullity, Rank, and Invertibility of Linear Combinations of k-Potent Matrices" in Mathematics, 8, no. 12 (2020):2147,
https://doi.org/10.3390/math8122147 . .

Noise-Indicator Arma Model with Application in Fitting Physically-Based Time Series

Stojanović, Vladica; Kevkić, Tijana; Ljajko, Eugen; Jelić, Gordana

(University Politehnica of Bucharest, 2019)

TY  - JOUR
AU  - Stojanović, Vladica
AU  - Kevkić, Tijana
AU  - Ljajko, Eugen
AU  - Jelić, Gordana
PY  - 2019
UR  - https://www.scientificbulletin.upb.ro/rev_docs_arhiva/rez083_245254.pdf
UR  - http://jakov.kpu.edu.rs/handle/123456789/974
AB  - In this paper we propose modification of a linear autoregressive moving-average (ARMA) model by using the so-called Noise-Indicator time series. The obtained model, named NIN–ARMA model, is nonlinear threshold autoregressive one. The basic stochastic properties of the NIN–ARMA model have been analyzed and the Empirical Characteristic Function (ECF) method has been used for parameters estimation. Finally, the NIN–ARMA model has been applied in fitting of two actual, real-based physical time series.
PB  - University Politehnica of Bucharest
T2  - U.P.B. Scientific Bulletin-Series A: Applied Mathematics & Physics
T1  - Noise-Indicator Arma Model with Application in Fitting Physically-Based Time Series
VL  - 81
IS  - 2
SP  - 257
EP  - 264
UR  - https://hdl.handle.net/21.15107/rcub_jakov_974
ER  - 
@article{
author = "Stojanović, Vladica and Kevkić, Tijana and Ljajko, Eugen and Jelić, Gordana",
year = "2019",
abstract = "In this paper we propose modification of a linear autoregressive moving-average (ARMA) model by using the so-called Noise-Indicator time series. The obtained model, named NIN–ARMA model, is nonlinear threshold autoregressive one. The basic stochastic properties of the NIN–ARMA model have been analyzed and the Empirical Characteristic Function (ECF) method has been used for parameters estimation. Finally, the NIN–ARMA model has been applied in fitting of two actual, real-based physical time series.",
publisher = "University Politehnica of Bucharest",
journal = "U.P.B. Scientific Bulletin-Series A: Applied Mathematics & Physics",
title = "Noise-Indicator Arma Model with Application in Fitting Physically-Based Time Series",
volume = "81",
number = "2",
pages = "257-264",
url = "https://hdl.handle.net/21.15107/rcub_jakov_974"
}
Stojanović, V., Kevkić, T., Ljajko, E.,& Jelić, G.. (2019). Noise-Indicator Arma Model with Application in Fitting Physically-Based Time Series. in U.P.B. Scientific Bulletin-Series A: Applied Mathematics & Physics
University Politehnica of Bucharest., 81(2), 257-264.
https://hdl.handle.net/21.15107/rcub_jakov_974
Stojanović V, Kevkić T, Ljajko E, Jelić G. Noise-Indicator Arma Model with Application in Fitting Physically-Based Time Series. in U.P.B. Scientific Bulletin-Series A: Applied Mathematics & Physics. 2019;81(2):257-264.
https://hdl.handle.net/21.15107/rcub_jakov_974 .
Stojanović, Vladica, Kevkić, Tijana, Ljajko, Eugen, Jelić, Gordana, "Noise-Indicator Arma Model with Application in Fitting Physically-Based Time Series" in U.P.B. Scientific Bulletin-Series A: Applied Mathematics & Physics, 81, no. 2 (2019):257-264,
https://hdl.handle.net/21.15107/rcub_jakov_974 .