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Publications (10 of 12) Show all publications
Ghorbani, M., Vafaei, N., Dvořák, J. & Myllymäki, M. (2021). Testing the first-order separability hypothesis for spatio-temporal point patterns. Computational Statistics & Data Analysis, 161, Article ID 107245.
Open this publication in new window or tab >>Testing the first-order separability hypothesis for spatio-temporal point patterns
2021 (English)In: Computational Statistics & Data Analysis, ISSN 0167-9473, E-ISSN 1872-7352, Vol. 161, article id 107245Article in journal (Refereed) Published
Abstract [en]

First-order separability of a spatio-temporal point process plays a fundamental role in the analysis of spatio-temporal point pattern data. While it is often a convenient assumption that simplifies the analysis greatly, existing non-separable structures should be accounted for in the model construction. Three different tests are proposed to investigate this hypothesis as a step of preliminary data analysis. The first two tests are exact or asymptotically exact for Poisson processes. The first test based on permutations and global envelopes allows one to detect at which spatial and temporal locations or lags the data deviate from the null hypothesis. The second test is a simple and computationally cheap X2-test. The third test is based on stochastic reconstruction method and can be generally applied for non-Poisson processes. The performance of the first two tests is studied in a simulation study for Poisson and non-Poisson models. The third test is applied to the real data of the UK 2001 epidemic foot and mouth disease.

Place, publisher, year, edition, pages
Elsevier, 2021
Keywords
Global envelope, Log Gaussian Cox processes, Kernel estimation, Permutation, Separability of intensity function, Stochastic reconstruction
National Category
Probability Theory and Statistics
Identifiers
urn:nbn:se:ltu:diva-95430 (URN)10.1016/j.csda.2021.107245 (DOI)000656871500014 ()2-s2.0-85103965352 (Scopus ID)
Funder
The Kempe Foundations, SMK-1750
Note

Funder: Academy of Finland (295100, 306875, 327211); Czech Republic (19-04412S)

Available from: 2023-01-30 Created: 2023-01-30 Last updated: 2023-09-06Bibliographically approved
Ghorbani, M., Cronie, O., Mateu, J. & Yu, J. (2020). Functional marked point processes: a natural structure to unify spatio-temporal frameworks and to analyse dependent functional data. Test (Madrid), 30(3), 529-568
Open this publication in new window or tab >>Functional marked point processes: a natural structure to unify spatio-temporal frameworks and to analyse dependent functional data
2020 (English)In: Test (Madrid), ISSN 1133-0686, E-ISSN 1863-8260, Vol. 30, no 3, p. 529-568Article in journal (Refereed) Published
Abstract [en]

This paper treats functional marked point processes (FMPPs), which are defined as marked point processes where the marks are random elements in some (Polish) function space. Such marks may represent, for example, spatial paths or functions of time. To be able to consider, for example, multivariate FMPPs, we also attach an additional, Euclidean, mark to each point. We indicate how the FMPP framework quite naturally connects the point process framework with both the functional data analysis framework and the geostatistical framework. We further show that various existing stochastic models fit well into the FMPP framework. To be able to carry out nonparametric statistical analyses for FMPPs, we study characteristics such as product densities and Palm distributions, which are the building blocks for many summary statistics. We proceed to defining a new family of summary statistics, so-called weighted marked reduced moment measures, together with their nonparametric estimators, in order to study features of the functional marks. We further show how other summary statistics may be obtained as special cases of these summary statistics. We finally apply these tools to analyse population structures, such as demographic evolution and sex ratio over time, in Spanish provinces. 

Place, publisher, year, edition, pages
Springer, 2020
National Category
Computer Sciences
Identifiers
urn:nbn:se:ltu:diva-95447 (URN)10.1007/s11749-020-00730-2 (DOI)000562663300001 ()2-s2.0-85089870331 (Scopus ID)
Funder
The Kempe Foundations, SMK-1750
Available from: 2023-01-31 Created: 2023-01-31 Last updated: 2023-10-28Bibliographically approved
Vosoughi, A., Sadigh-Eteghad, S., Ghorbani, M., Shahmorad, S., Farhoudi, M., Rafi, M. A. & Omidi, Y. (2020). Mathematical Models to Shed Light on Amyloid-Beta and Tau Protein Dependent Pathologies in Alzheimer’s Disease. Neuroscience, 424, 45-57
Open this publication in new window or tab >>Mathematical Models to Shed Light on Amyloid-Beta and Tau Protein Dependent Pathologies in Alzheimer’s Disease
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2020 (English)In: Neuroscience, ISSN 0306-4522, E-ISSN 1873-7544, Vol. 424, p. 45-57Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Elsevier, 2020
National Category
Neurosciences
Identifiers
urn:nbn:se:ltu:diva-95450 (URN)10.1016/j.neuroscience.2019.09.017 (DOI)000505150700005 ()31682825 (PubMedID)2-s2.0-85075453047 (Scopus ID)
Available from: 2023-01-31 Created: 2023-01-31 Last updated: 2023-05-08Bibliographically approved
Møller, J. & Ghorbani, M. (2015). Functional summary statistics for the Johnson–Mehl model. Journal of Statistical Computation and Simulation, 85(5), 899-916
Open this publication in new window or tab >>Functional summary statistics for the Johnson–Mehl model
2015 (English)In: Journal of Statistical Computation and Simulation, ISSN 0094-9655, E-ISSN 1563-5163, Vol. 85, no 5, p. 899-916Article in journal (Refereed) Published
Abstract [en]

The Johnson–Mehl germination-growth model is a spatio-temporal point process model which among other things have been used for the description of neurotransmitters datasets. However, for such datasets parametric Johnson–Mehl models fitted by maximum likelihood have yet not been evaluated by means of functional summary statistics. This paper therefore invents four functional summary statistics adapted to the Johnson–Mehl model, with two of them based on the second-order properties and the other two on the nuclei-boundary distances for the associated Johnson–Mehl tessellation. The functional summary statistics theoretical properties are investigated, non-parametric estimators are suggested, and their usefulness for model checking is examined in a simulation study. The functional summary statistics are also used for checking fitted parametric Johnson–Mehl models for a neurotransmitters dataset.

Place, publisher, year, edition, pages
Taylor & Francis, 2015
National Category
Probability Theory and Statistics
Identifiers
urn:nbn:se:ltu:diva-95431 (URN)10.1080/00949655.2013.850691 (DOI)000347544600003 ()2-s2.0-84920640861 (Scopus ID)
Available from: 2023-01-30 Created: 2023-01-30 Last updated: 2023-05-08Bibliographically approved
Møller, J., Ghorbani, M. & Rubak, E. (2015). Mechanistic spatio-temporal point process models for marked point processes, with a view to forest stand data. Biometrics, 72(3), 687-696
Open this publication in new window or tab >>Mechanistic spatio-temporal point process models for marked point processes, with a view to forest stand data
2015 (English)In: Biometrics, ISSN 0006-341X, E-ISSN 1541-0420, Vol. 72, no 3, p. 687-696Article in journal (Refereed) Published
Place, publisher, year, edition, pages
John Wiley & Sons, 2015
National Category
Forest Science
Identifiers
urn:nbn:se:ltu:diva-95451 (URN)10.1111/biom.12466 (DOI)000383369000003 ()26689438 (PubMedID)2-s2.0-85027937107 (Scopus ID)
Available from: 2023-01-31 Created: 2023-01-31 Last updated: 2023-05-08Bibliographically approved
Rodríguez-Corté, F. J., Ghorbani, M., Mateu, J. & Stoyan, D. (2014). On the expected value and variance for an estimator of the spatio-temporal product density function. Centre for Stochastic Geometry and Advanced Bioimaging, Aarhus University
Open this publication in new window or tab >>On the expected value and variance for an estimator of the spatio-temporal product density function
2014 (English)Report (Other academic)
Place, publisher, year, edition, pages
Centre for Stochastic Geometry and Advanced Bioimaging, Aarhus University, 2014
Series
CSGB Research Reports ; 6
National Category
Probability Theory and Statistics
Identifiers
urn:nbn:se:ltu:diva-95452 (URN)
Available from: 2023-01-31 Created: 2023-01-31 Last updated: 2024-06-26Bibliographically approved
Ghorbani, M. (2013). Cauchy cluster process. Metrika (Heidelberg), 76(5), 697-706
Open this publication in new window or tab >>Cauchy cluster process
2013 (English)In: Metrika (Heidelberg), ISSN 0026-1335, E-ISSN 1435-926X, Vol. 76, no 5, p. 697-706Article in journal (Refereed) Published
Abstract [en]

In this paper we introduce an instance of the well-know Neyman–Scott cluster process model with clusters having a long tail behaviour. In our model the offspring points are distributed around the parent points according to a circular Cauchy distribution. Using a modified Cramér-von Misses test statistic and the simulated pointwise envelopes it is shown that this model fits better than the Thomas process to the frequently analyzed long-leaf pine data-set.

Place, publisher, year, edition, pages
Springer, 2013
National Category
Probability Theory and Statistics
Identifiers
urn:nbn:se:ltu:diva-95432 (URN)10.1007/s00184-012-0411-y (DOI)000320673900005 ()2-s2.0-84879209046 (Scopus ID)
Available from: 2023-01-30 Created: 2023-01-30 Last updated: 2023-05-08Bibliographically approved
Ghorbani, M. (2013). Testing the weak stationarity of a spatio-temporal point process. Stochastic environmental research and risk assessment (Print), 27(2), 517-524
Open this publication in new window or tab >>Testing the weak stationarity of a spatio-temporal point process
2013 (English)In: Stochastic environmental research and risk assessment (Print), ISSN 1436-3240, E-ISSN 1436-3259, Vol. 27, no 2, p. 517-524Article in journal (Refereed) Published
Abstract [en]

A common assumption in analyzing spatial and spatio-temporal point processes is stationarity, while in many real applications because of the environmental effects the stationarity condition is not often met. We propose two types of test statistics to test stationarity for spatio-temporal point processes, by adapting, Palahi, Pukkala & Mateu (2009) and by considering the square difference between observed and expected (under stationarity) intensities. We study the efficiency of the new statistics by simulated data, and we apply them to test the stationarity of real data.

Place, publisher, year, edition, pages
Springer, 2013
National Category
Probability Theory and Statistics
Identifiers
urn:nbn:se:ltu:diva-95435 (URN)10.1007/s00477-012-0597-6 (DOI)000313657100017 ()2-s2.0-84872486325 (Scopus ID)
Available from: 2023-01-30 Created: 2023-01-30 Last updated: 2023-05-08Bibliographically approved
Møller, J. & Ghorbani, M. (2012). Aspects of second-order analysis of structured inhomogeneous spatio-temporal point processes. Statistica Neerlandica, 66(4), 472-491
Open this publication in new window or tab >>Aspects of second-order analysis of structured inhomogeneous spatio-temporal point processes
2012 (English)In: Statistica Neerlandica, ISSN 0039-0402, E-ISSN 1467-9574, Vol. 66, no 4, p. 472-491Article in journal (Refereed) Published
Abstract [en]

Statistical methodology for spatio-temporal point processes is in its infancy. We consider second-order analysis based on pair correlation functions and K-functions for general inhomogeneous spatio-temporal point processes and for inhomogeneous spatio-temporal Cox processes. Assuming spatio-temporal separability of the intensity function, we clarify different meanings of second-order spatio-temporal separability. One is second-order spatio-temporal independence and relates to log-Gaussian Cox processes with an additive covariance structure of the underlying spatio-temporal Gaussian process. Another concerns shot-noise Cox processes with a separable spatio-temporal covariance density. We propose diagnostic procedures for checking hypotheses of second-order spatio-temporal separability, which we apply on simulated and real data.

Place, publisher, year, edition, pages
John Wiley & Sons, 2012
National Category
Probability Theory and Statistics
Identifiers
urn:nbn:se:ltu:diva-95436 (URN)10.1111/j.1467-9574.2012.00526.x (DOI)000309746400007 ()2-s2.0-84867398452 (Scopus ID)
Available from: 2023-01-30 Created: 2023-01-30 Last updated: 2023-05-08Bibliographically approved
Ghorbani, M. (2005). Maximum Entropy-Based Fuzzy Clustering by Using L_1-norm Space. Turkish Journal of Mathematics, 29(4), Article ID 9.
Open this publication in new window or tab >>Maximum Entropy-Based Fuzzy Clustering by Using L_1-norm Space
2005 (English)In: Turkish Journal of Mathematics, ISSN 1300-0098, E-ISSN 1303-6149, Vol. 29, no 4, article id 9Article in journal (Refereed) Published
Place, publisher, year, edition, pages
TÜBİTAK Academic Journals, 2005
National Category
Probability Theory and Statistics
Identifiers
urn:nbn:se:ltu:diva-95454 (URN)
Available from: 2023-01-31 Created: 2023-01-31 Last updated: 2023-01-31Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0855-0288

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