@article{ceyhan_2018, title={A contingency table approach based on nearest neighbour relations for testing self and mixed correspondence}, volume={42}, ISSN={["2013-8830"]}, DOI={10.2436/20.8080.02.72}, number={2}, journal={SORT-STATISTICS AND OPERATIONS RESEARCH TRANSACTIONS}, author={Ceyhan, Elvan}, year={2018}, pages={125–157} }
 @article{ceyhan_2017, title={Cell-specific and post-hoc spatial clustering tests based on nearest neighbor contingency tables}, volume={46}, ISSN={1226-3192}, url={http://dx.doi.org/10.1016/J.JKSS.2016.10.002}, DOI={10.1016/J.JKSS.2016.10.002}, number={2}, journal={Journal of the Korean Statistical Society}, publisher={Elsevier BV}, author={Ceyhan, Elvan}, year={2017}, month={Jun}, pages={219–245} }
 @article{ceyhan_bahadır_2017, title={Nearest neighbor methods for testing reflexivity}, volume={24}, ISSN={1352-8505 1573-3009}, url={http://dx.doi.org/10.1007/S10651-016-0361-Z}, DOI={10.1007/S10651-016-0361-Z}, number={1}, journal={Environmental and Ecological Statistics}, publisher={Springer Science and Business Media LLC}, author={Ceyhan, Elvan and Bahadır, Selim}, year={2017}, month={Mar}, pages={69–108} }
 @article{ceyhan_2016, title={Edge density of new graph types based on a random digraph family}, volume={33}, ISSN={1572-3127}, url={http://dx.doi.org/10.1016/J.STAMET.2016.07.003}, DOI={10.1016/J.STAMET.2016.07.003}, abstractNote={We consider two types of graphs based on a family of proximity catch digraphs (PCDs) and study their edge density. In particular, the PCDs we use are a parameterized digraph family called proportional-edge (PE) PCDs and the two associated graph types are the “underlying graphs” and the newly introduced “reflexivity graphs” based on the PE-PCDs. These graphs are extensions of random geometric graphs where distance is replaced with a dissimilarity measure and the threshold is not fixed but depends on the location of the points. PCDs and the associated graphs are constructed based on data points from two classes, say X and Y, where one class (say class X) forms the vertices of the PCD and the Delaunay tessellation of the other class (i.e., class Y) yields the (Delaunay) cells which serve as the support of class X points. We demonstrate that edge density of these graphs is a U-statistic, hence obtain the asymptotic normality of it for data from any distribution that satisfies mild regulatory conditions. The rate of convergence to asymptotic normality is sharper for the edge density of the reflexivity and underlying graphs compared to the arc density of the PE-PCDs. For uniform data in Euclidean plane where Delaunay cells are triangles, we demonstrate that the distribution of the edge density is geometry invariant (i.e., independent of the shape of the triangular support). We compute the explicit forms of the asymptotic normal distribution for uniform data in one Delaunay triangle in the Euclidean plane utilizing this geometry invariance property. We also provide various versions of edge density in the multiple triangle case. The approach presented here can also be extended for application to data in higher dimensions.}, journal={Statistical Methodology}, publisher={Elsevier BV}, author={Ceyhan, Elvan}, year={2016}, month={Dec}, pages={31–54} }
 @article{erdem_ceyhan_varli_2014, title={A new correlation coefficient for bivariate time-series data}, volume={414}, ISSN={0378-4371}, url={http://dx.doi.org/10.1016/J.PHYSA.2014.07.054}, DOI={10.1016/J.PHYSA.2014.07.054}, abstractNote={The correlation in time series has received considerable attention in the literature. Its use has attained an important role in the social sciences and finance. For example, pair trading in finance is concerned with the correlation between stock prices, returns, etc. In general, Pearson’s correlation coefficient is employed in these areas although it has many underlying assumptions which restrict its use. Here, we introduce a new correlation coefficient which takes into account the lag difference of data points. We investigate the properties of this new correlation coefficient. We demonstrate that it is more appropriate for showing the direction of the covariation of the two variables over time. We also compare the performance of the new correlation coefficient with Pearson’s correlation coefficient and Detrended Cross-Correlation Analysis (DCCA) via simulated examples.}, journal={Physica A: Statistical Mechanics and its Applications}, publisher={Elsevier BV}, author={Erdem, Orhan and Ceyhan, Elvan and Varli, Yusuf}, year={2014}, month={Nov}, pages={274–284} }
 @article{ceyhan_2014, title={Comparison of relative density of two random geometric digraph families in testing spatial clustering}, volume={23}, ISSN={1133-0686 1863-8260}, url={http://dx.doi.org/10.1007/S11749-013-0344-4}, DOI={10.1007/S11749-013-0344-4}, number={1}, journal={TEST}, publisher={Springer Science and Business Media LLC}, author={Ceyhan, Elvan}, year={2014}, month={Mar}, pages={100–134} }
 @article{suzuki_takayanagi_wentz_takayanagi_schretlen_ceyhan_sawa_barta_ratnanather_cascella_2014, title={Poster #T228 REDUCED ANTERIOR CINGULATE GRAY MATTER VOLUME AND THICKNESS IN SUBJECTS WITH DEFICIT SCHIZOPHRENIA}, volume={153}, ISSN={0920-9964}, url={http://dx.doi.org/10.1016/S0920-9964(14)71044-8}, DOI={10.1016/S0920-9964(14)71044-8}, abstractNote={The Uchkoshkon tin deposit is one of the largest deposits in the Sn–W Saryjaz ore district of Eastern Kyrgyzstan. The district coincides spatially with the Saryjaz syntaxis, which is the narrowest portion of the South Tien Shan collisional belt. The syntaxis is distinguished by collisional thrust tectonics and postcollisional A-type granite magmatism of Permian age. The Uchkoshkon deposit is in the exocontact zone of a 260-km2, 273–279 Ma, ilmenite series, high heat production, biotite granite pluton. A satellite granite stock (400 × 250 m) and an explosive breccia pipe (450 × 150 m), crosscutting the stock, are the central structural features of the deposit area. The main stock, accompanied by Li–F felsite dykes, controlled early-stage Mo–W and Sn–W greisen–stockwork mineralization that surrounds the apical portion of the stock. The breccia pipe postdates the emplacement of the Li–F felsite dykes and greisen–stockwork mineralization. The pipe is rooted in main pluton and has been traced by a borehole to a depth of 800 m. The breccia was injected by a swarm of tree-like branching dykes with diffuse contours consisting of K- and B-rich rhyolite porphyry cementing the breccia fragments. The main breccia body has been intruded by a much smaller (150 × 100 m) hydrothermal breccia pipe with quartz–tourmaline matrix, which immediately preceded main-stage lode mineralization. The majority of the lodes occur outside the breccia pipe within a zone of pervasive scapolitization that surrounds the main pluton. The main-stage lodes are represented by quartz–tourmaline–cassiterite veins with minor sulfides, which occupy a series of steeply-dipping, near-parallel, north–northeast-trending shear fractures that are related to postcollisional strike-slip tectonics. Where quartz–tourmaline–cassiterite veins crosscut moderately-dipping skarn deposits, the latter are commercially mineralized with cassiterite, nordenskioldine and borosilicate minerals. The formation of both explosive breccia and main-stage lode mineralization was related to the evolution of B- and H2O-rich residual magma deep within the main pluton. The suggested formation model of the Uchkoshkon tin deposit is generally applicable to other major Sn- and Sn–W deposits in the Saryjaz ore district.}, journal={Schizophrenia Research}, publisher={Elsevier BV}, author={Suzuki, Michio and Takayanagi, Mizuho and Wentz, Jacqueline and Takayanagi, Yoichiro and Schretlen, David and Ceyhan, Elvan and Sawa, Akira and Barta, Patrick and Ratnanather, Tilak and Cascella, Nicola}, year={2014}, month={Apr}, pages={S370} }
 @article{ceyhan_2014, title={Segregation indices for disease clustering}, volume={33}, ISSN={0277-6715}, url={http://dx.doi.org/10.1002/SIM.6053}, DOI={10.1002/SIM.6053}, abstractNote={Spatial clustering has important implications in various fields. In particular, disease clustering is of major public concern in epidemiology. In this article, we propose the use of two distance‐based segregation indices to test the significance of disease clustering among subjects whose locations are from a homogeneous or an inhomogeneous population. We derive the asymptotic distributions of the segregation indices and compare them with other distance‐based disease clustering tests in terms of empirical size and power by extensive Monte Carlo simulations. The null pattern we consider is the random labeling (RL) of cases and controls to the given locations. Along this line, we investigate the sensitivity of the size of these tests to the underlying background pattern (e.g., clustered or homogenous) on which the RL is applied, the level of clustering and number of clusters, or to differences in relative abundances of the classes. We demonstrate that differences in relative abundances have the highest influence on the empirical sizes of the tests. We also propose various non‐RL patterns as alternatives to the RL pattern and assess the empirical power performances of the tests under these alternatives. We observe that the empirical size of one of the indices is more robust to the differences in relative abundances, and this index performs comparable with the best performers in literature in terms of power. We illustrate the methods on two real‐life examples from epidemiology. Copyright © 2013 John Wiley & Sons, Ltd.}, number={10}, journal={Statistics in Medicine}, publisher={Wiley}, author={Ceyhan, Elvan}, year={2014}, month={May}, pages={1662–1684} }
 @article{ceyhan_2014, title={Simulation and characterization of multi-class spatial patterns from stochastic point processes of randomness, clustering and regularity}, volume={28}, ISSN={1436-3240 1436-3259}, url={http://dx.doi.org/10.1007/S00477-013-0824-9}, DOI={10.1007/S00477-013-0824-9}, number={5}, journal={Stochastic Environmental Research and Risk Assessment}, publisher={Springer Science and Business Media LLC}, author={Ceyhan, Elvan}, year={2014}, month={Jul}, pages={1277–1306} }
 @article{ceyhan_ertuğay_düzgün_2013, title={Exploratory and inferential methods for spatio-temporal analysis of residential fire clustering in urban areas}, volume={58}, ISSN={0379-7112}, url={http://dx.doi.org/10.1016/J.FIRESAF.2013.01.024}, DOI={10.1016/J.FIRESAF.2013.01.024}, abstractNote={The spatio-temporal analysis of residential fires could allow decision makers to plan effective resource allocations in fire management according to fire clustering levels in space and time. In this study, we provide guidelines for the use of various methods in detecting the differences in clustering patterns of fire and non-fire (i.e., background residential) locations and how these patterns change over time. As a preliminary analysis step, various exploratory data analysis methods, such as, intensity plots (i.e., kernel density estimates) are used. Moreover, the use of Diggle's-function (a second order analysis technique) is proposed for detecting the clustering of residential fire locations (if any) and whether there is additional clustering (or regularity) in the locations of the fires compared to background residential pattern. A test for trend over time (in years, months, and weeks) of the fire location patterns are provided with a space–time interaction analysis by the spatio-temporal-function. Residential fire data from Çankaya Municipality of Ankara, Turkey is used as an illustrative example. The presented methodology is also applicable to residential fire data from similar urban settings.}, journal={Fire Safety Journal}, publisher={Elsevier BV}, author={Ceyhan, Elvan and Ertuğay, Kıvanç and Düzgün, Şebnem}, year={2013}, month={May}, pages={226–239} }
 @article{ratnanather_poynton_pisano_crocker_postell_cebron_ceyhan_honeycutt_mahon_barta_2013, title={Morphometry of superior temporal gyrus and planum temporale in schizophrenia and psychotic bipolar disorder}, volume={150}, ISSN={0920-9964}, url={http://dx.doi.org/10.1016/J.SCHRES.2013.08.014}, DOI={10.1016/J.SCHRES.2013.08.014}, abstractNote={Structural abnormalities in temporal lobe, including the superior temporal gyrus (STG) and planum temporale (PT), have been reported in schizophrenia (SCZ) and bipolar disorder (BPD) patients. While most MRI studies have suggested gray matter volume and surface area reduction in temporal lobe regions, few have explored changes in laminar thickness in PT and STG in SCZ and BPD. ROI subvolumes of the STG from 94 subjects were used to yield gray matter volume, gray/white surface area and laminar thickness for STG and PT cortical regions. Morphometric analysis suggests that there may be gender and laterality effects on the size and shape of the PT in BPD (n = 36) and SCZ (n = 31) with reduced laterality in PT in subjects with SCZ but not in BPD. In addition, PT surface area was seen to be larger in males, and asymmetry in PT surface area was larger in BPD. Subjects with SCZ had reduced thickness and smaller asymmetry in PT volume. Thus, the PT probably plays a more sensitive role than the STG in structural abnormalities seen in SCZ.}, number={2-3}, journal={Schizophrenia Research}, publisher={Elsevier BV}, author={Ratnanather, J. Tilak and Poynton, Clare B. and Pisano, Dominic V. and Crocker, Britni and Postell, Elizabeth and Cebron, Shannon and Ceyhan, Elvan and Honeycutt, Nancy A. and Mahon, Pamela B. and Barta, Patrick E.}, year={2013}, month={Nov}, pages={476–483} }
 @article{takayanagi_wentz_takayanagi_schretlen_ceyhan_wang_suzuki_sawa_barta_ratnanather_et al._2013, title={Reduced anterior cingulate gray matter volume and thickness in subjects with deficit schizophrenia}, volume={150}, ISSN={0920-9964}, url={http://dx.doi.org/10.1016/J.SCHRES.2013.07.036}, DOI={10.1016/J.SCHRES.2013.07.036}, abstractNote={Patients with deficit schizophrenia (D-SZ) differ from patients with the non-deficit form of schizophrenia (ND-SZ) in several aspects such as risk factors, neurobiological correlates, treatment response and clinical outcome. It has been debated if brain morphology could differentiate D-SZ from ND-SZ. Anterior cingulate gyrus (ACG) region regulates cognitive and emotional processing and past studies reported structural changes in this region in patients with SZ.1.5-T 3D MRI scans were obtained from 18 D-SZ patients, 30 ND-SZ patients and 82 healthy controls (HCs). We used FreeSurfer-initalized labeled cortical distance mapping (FSLCDM) to measure ACG gray matter volume, cortical thickness, and area of the gray/white interface. Furthermore, cortical thickness was compared among the 3 groups using the pooled labeled cortical distance mapping (LCDM) method.The ACG cortex of the D-SZ group was thinner than the ND-SZ group. Pooled LCDM demonstrated that the ACG cortex was bilaterally thinner in both the ND-SZ group and the D-SZ group compared with the control group. The right ACG gray matter volume was significantly reduced in D-SZ patients as compared with healthy controls (p=0.005 CONCLUSION: Our data suggest that qualitative, categorical differences in neuroanatomy may distinguish between deficit and non-deficit subtypes of schizophrenia.}, number={2-3}, journal={Schizophrenia Research}, publisher={Elsevier BV}, author={Takayanagi, Mizuho and Wentz, Jacqueline and Takayanagi, Yoichiro and Schretlen, David J. and Ceyhan, Elvan and Wang, Lei and Suzuki, Michio and Sawa, Akira and Barta, Patrick E and Ratnanather, J. Tilak and et al.}, year={2013}, month={Nov}, pages={484–490} }
 @article{coskun_ceyhan_inal_serteser_unsal_2013, title={The comparison of parametric and nonparametric bootstrap methods for reference interval computation in small sample size groups}, volume={18}, ISSN={0949-1775 1432-0517}, url={http://dx.doi.org/10.1007/S00769-012-0948-5}, DOI={10.1007/S00769-012-0948-5}, number={1}, journal={Accreditation and Quality Assurance}, publisher={Springer Science and Business Media LLC}, author={Coskun, Abdurrahman and Ceyhan, Elvan and Inal, Tamer C. and Serteser, Mustafa and Unsal, Ibrahim}, year={2013}, month={Feb}, pages={51–60} }
 @article{ceyhan_xu_gurkan_emre_turali_el assal_acikgenc_wu_demirci_2012, title={Prediction and control of number of cells in microdroplets by stochastic modeling}, volume={12}, ISSN={1473-0197 1473-0189}, url={http://dx.doi.org/10.1039/c2lc40523g}, DOI={10.1039/c2lc40523g}, abstractNote={Manipulation and encapsulation of cells in microdroplets has found many applications in various fields such as clinical diagnostics, pharmaceutical research, and regenerative medicine. The control over the number of cells in individual droplets is important especially for microfluidic and bioprinting applications. There is a growing need for modeling approaches that enable control over a number of cells within individual droplets. In this study, we developed statistical models based on negative binomial regression to determine the dependence of number of cells per droplet on three main factors: cell concentration in the ejection fluid, droplet size, and cell size. These models were based on experimental data obtained by using a microdroplet generator, where the presented statistical models estimated the number of cells encapsulated in droplets. We also propose a stochastic model for the total volume of cells per droplet. The statistical and stochastic models introduced in this study are adaptable to various cell types and cell encapsulation technologies such as microfluidic and acoustic methods that require reliable control over number of cells per droplet provided that settings and interaction of the variables is similar.}, number={22}, journal={Lab on a Chip}, publisher={Royal Society of Chemistry (RSC)}, author={Ceyhan, Elvan and Xu, Feng and Gurkan, Umut Atakan and Emre, Ahmet Emrehan and Turali, Emine Sumeyra and El Assal, Rami and Acikgenc, Ali and Wu, Chung-an Max and Demirci, Utkan}, year={2012}, pages={4884} }
 @article{ceyhan_2012, title={The distribution of the relative arc density of a family of interval catch digraph based on uniform data}, volume={75}, ISSN={0026-1335 1435-926X}, url={http://dx.doi.org/10.1007/S00184-011-0351-Y}, DOI={10.1007/S00184-011-0351-Y}, number={6}, journal={Metrika}, publisher={Springer Science and Business Media LLC}, author={Ceyhan, Elvan}, year={2012}, month={Aug}, pages={761–793} }
 @article{ceyhan_beg_cerito˜glu_wang_morris_csernansky_miller_ratnanather_2011, title={Quantization and analysis of hippocampal morphometric changes due to dementia of Alzheimer type using metric distances based on large deformation diffeomorphic metric mapping}, volume={35}, ISSN={0895-6111}, url={http://dx.doi.org/10.1016/j.compmedimag.2011.01.005}, DOI={10.1016/j.compmedimag.2011.01.005}, abstractNote={The metric distance obtained from the large deformation diffeomorphic metric mapping (LDDMM) algorithm is used to quantize changes in morphometry of brain structures due to neuropsychiatric diseases. For illustrative purposes we consider changes in hippocampal morphometry (shape and size) due to very mild dementia of the Alzheimer type (DAT). LDDMM, which was previously used to calculate dense one-to-one correspondence vector fields between hippocampal shapes, measures the morphometric differences with respect to a template hippocampus by assigning metric distances on the space of anatomical images thereby allowing for direct comparison of morphometric differences. We characterize what information the metric distances provide in terms of size and shape given the hippocampal, brain and intracranial volumes. We demonstrate that metric distance is a measure of morphometry (i.e., shape and size) but mostly a measure of shape, while volume is mostly a measure of size. Moreover, we show how metric distances can be used in cross-sectional, longitudinal analysis, as well as left-right asymmetry comparisons, and provide how the metric distances can serve as a discriminative tool using logistic regression. Thus, we show that metric distances with respect to a template computed via LDDMM can be a powerful tool in detecting differences in shape.}, number={4}, journal={Computerized Medical Imaging and Graphics}, publisher={Elsevier BV}, author={Ceyhan, Elvan and Beg, Mirza Faisal and Cerito˜glu, Can and Wang, Lei and Morris, John C. and Csernansky, John G. and Miller, Michael I. and Ratnanather, J.Tilak}, year={2011}, month={Jun}, pages={275–293} }
 @article{ceyhan_2011, title={Spatial Clustering Tests Based on the Domination Number of a New Random Digraph Family}, volume={40}, ISSN={0361-0926 1532-415X}, url={http://dx.doi.org/10.1080/03610921003597211}, DOI={10.1080/03610921003597211}, abstractNote={We use the domination number of a parametrized random digraph family called proportional-edge proximity catch digraphs (PCDs) for testing multivariate spatial point patterns. This digraph family is based on relative positions of data points from various classes. We extend the results on the distribution of the domination number of proportional-edge PCDs, and use the domination number as a statistic for testing segregation and association against complete spatial randomness. We demonstrate that the domination number of the PCD has binomial distribution when size of one class is fixed while the size of the other (whose points constitute the vertices of the digraph) tends to infinity and has asymptotic normality when sizes of both classes tend to infinity. We evaluate the finite sample performance of the test by Monte Carlo simulations and prove the consistency of the test under the alternatives. We find the optimal parameters for testing each of the segregation and association alternatives. Furthermore, the methodology discussed in this article is valid for data in higher dimensions also.}, number={8}, journal={Communications in Statistics - Theory and Methods}, publisher={Informa UK Limited}, author={Ceyhan, Elvan}, year={2011}, month={Mar}, pages={1363–1395} }
 @article{ceyhan_hosakere_nishino_alexopoulos_todd_botteron_miller_ratnanather_2011, title={Statistical Analysis of Cortical Morphometrics Using Pooled Distances Based on Labeled Cortical Distance Maps}, volume={40}, ISSN={0924-9907 1573-7683}, url={http://dx.doi.org/10.1007/S10851-010-0240-4}, DOI={10.1007/S10851-010-0240-4}, abstractNote={Neuropsychiatric disorders have been demonstrated to manifest shape differences in cortical structures. Labeled Cortical Distance Mapping (LCDM) is a powerful tool in quantifying such morphometric differences and characterizes the morphometry of the laminar cortical mantle of cortical structures. Specifically, LCDM data are distances of labeled gray matter (GM) voxels with respect to the gray/white matter cortical surface. Volumes and descriptive measures (such as means and variances for each subject) based on LCDM distances provide descriptive summary information on some of the shape characteristics. However, additional morphometrics are contained in the data and their analysis may provide additional clues to underlying differences in cortical characteristics. To use more of this information, we pool (merge) LCDM distances from subjects in the same group. These pooled distances can help detect morphometric differences between groups, but do not provide information about the locations of such differences in the tissue in question. In this article, we check for the influence of the assumption violations on the analysis of pooled LCDM distances. We demonstrate that the classical parametric tests are robust to the non-normality and within sample dependence of LCDM distances and nonparametric tests are robust to within sample dependence of LCDM distances. We specify the types of alternatives for which the tests are more sensitive. We also show that the pooled LCDM distances provide powerful results for group differences in distribution of LCDM distances. As an illustrative example, we use GM in the ventral medial prefrontal cortex (VMPFC) in subjects with major depressive disorder (MDD), subjects at high risk (HR) of MDD, and healthy subjects. Significant morphometric differences were found in VMPFC due to MDD or being at HR. In particular, the analysis indicated that distances in left and right VMPFCs tend to decrease due to MDD or being at HR, possibly as a result of thinning. The methodology can also be applied to other cortical structures.}, number={1}, journal={Journal of Mathematical Imaging and Vision}, publisher={Springer Science and Business Media LLC}, author={Ceyhan, E. and Hosakere, M. and Nishino, T. and Alexopoulos, J. and Todd, R. D. and Botteron, K. N. and Miller, M. I. and Ratnanather, J. T.}, year={2011}, month={May}, pages={20–35} }
 @article{ceyhan_2010, title={An Investigation of New Graph Invariants Related to the Domination Number of Random Proximity Catch Digraphs}, volume={14}, ISSN={1387-5841 1573-7713}, url={http://dx.doi.org/10.1007/S11009-010-9204-9}, DOI={10.1007/S11009-010-9204-9}, number={2}, journal={Methodology and Computing in Applied Probability}, publisher={Springer Science and Business Media LLC}, author={Ceyhan, Elvan}, year={2010}, month={Nov}, pages={299–334} }
 @article{ceyhan_2010, title={Directional clustering tests based on nearest neighbour contingency tables}, volume={22}, ISSN={1048-5252 1029-0311}, url={http://dx.doi.org/10.1080/10485250903199861}, DOI={10.1080/10485250903199861}, abstractNote={Spatial interaction between two or more classes or species has important implications in various fields, and might cause multivariate patterns such as segregation or association. Segregation occurs when members of a class or species are more likely to be found near members of the same class or conspecifics; association occurs when members of a class or species are more likely to be found near members of another class or species. The null patterns considered are random labelling and complete spatial randomness (CSR) of points from two or more classes, which is henceforth called CSR independence. The clustering tests based on nearest neighbour contingency tables (NNCTs) that are in use in the literature are two-sided tests. In this article, we consider the directional (i.e. one-sided) versions of the cell-specific NNCT tests and introduce new directional NNCT tests for the two-class case. We analyse the distributional properties and compare the empirical significant levels and empirical power estimates of the tests using extensive Monte Carlo simulations. We demonstrate that the new directional tests have comparable performance with the currently available NNCT tests in terms of empirical size and power. We use an ecological data set for illustrative purposes and provide guidelines for using these NNCT tests.}, number={5}, journal={Journal of Nonparametric Statistics}, publisher={Informa UK Limited}, author={Ceyhan, Elvan}, year={2010}, month={Jul}, pages={599–616} }
 @article{ceyhan_2010, title={Extension of one-dimensional proximity regions to higher dimensions}, volume={43}, ISSN={0925-7721}, url={http://dx.doi.org/10.1016/j.comgeo.2010.05.002}, DOI={10.1016/j.comgeo.2010.05.002}, abstractNote={Proximity regions (and maps) are defined based on the relative allocation of points from two or more classes in an area of interest and are used to construct random graphs called proximity catch digraphs (PCDs) which have applications in various fields. The simplest of such maps is the spherical proximity map which gave rise to class cover catch digraph (CCCD) and was applied to pattern classification. In this article, we note some appealing properties of the spherical proximity map in compact intervals on the real line, thereby introduce the mechanism and guidelines for defining new proximity maps in higher dimensions. For non-spherical PCDs, Delaunay tessellation (triangulation in the real plane) is used to partition the region of interest in higher dimensions. We also introduce the auxiliary tools used for the construction of the new proximity maps, as well as some related concepts that will be used in the investigation and comparison of these maps and the resulting PCDs. We provide the distribution of graph invariants, namely, domination number and relative density, of the PCDs and characterize the geometry invariance of the distribution of these graph invariants for uniform data and provide some newly defined proximity maps in higher dimensions as illustrative examples.}, number={9}, journal={Computational Geometry}, publisher={Elsevier BV}, author={Ceyhan, Elvan}, year={2010}, month={Nov}, pages={721–748} }
 @article{ceyhan_goad_2009, title={A Comparison of Analysis of Covariate-Adjusted Residuals and Analysis of Covariance}, volume={38}, ISSN={0361-0918 1532-4141}, url={http://dx.doi.org/10.1080/03610910903243687}, DOI={10.1080/03610910903243687}, abstractNote={Various methods to control the influence of a covariate on a response variable are compared. These methods are ANOVA with or without homogeneity of variances (HOV) of errors and Kruskal–Wallis (K–W) tests on (covariate-adjusted) residuals and analysis of covariance (ANCOVA). Covariate-adjusted residuals are obtained from the overall regression line fit to the entire data set ignoring the treatment levels or factors. It is demonstrated that the methods on covariate-adjusted residuals are only appropriate when the regression lines are parallel and covariate means are equal for all treatments. Empirical size and power performance of the methods are compared by extensive Monte Carlo simulations. We manipulated the conditions such as assumptions of normality and HOV, sample size, and clustering of the covariates. The parametric methods on residuals and ANCOVA exhibited similar size and power when error terms have symmetric distributions with variances having the same functional form for each treatment, and covariates have uniform distributions within the same interval for each treatment. In such cases, parametric tests have higher power compared to the K–W test on residuals. When error terms have asymmetric distributions or have variances that are heterogeneous with different functional forms for each treatment, the tests are liberal with K–W test having higher power than others. The methods on covariate-adjusted residuals are severely affected by the clustering of the covariates relative to the treatment factors when covariate means are very different for treatments. For data clusters, ANCOVA method exhibits the appropriate level. However, such a clustering might suggest dependence between the covariates and the treatment factors, so makes ANCOVA less reliable as well.}, number={10}, journal={Communications in Statistics - Simulation and Computation}, publisher={Informa UK Limited}, author={Ceyhan, Elvan and Goad, Carla L.}, year={2009}, month={Sep}, pages={2019–2038} }
 @article{ceyhan_2009, title={Overall and pairwise segregation tests based on nearest neighbor contingency tables}, volume={53}, ISSN={0167-9473}, url={http://dx.doi.org/10.1016/j.csda.2008.08.002}, DOI={10.1016/j.csda.2008.08.002}, abstractNote={Multivariate interaction between two or more classes (or species) has important consequences in many fields and may cause multivariate clustering patterns such as spatial segregation or association. The spatial segregation occurs when members of a class tend to be found near members of the same class (i.e., near conspecifics) while spatial association occurs when members of a class tend to be found near members of the other class or classes. These patterns can be studied using a nearest neighbor contingency table (NNCT). The null hypothesis is randomness in the nearest neighbor (NN) structure, which may result from–among other patterns–random labeling (RL) or complete spatial randomness (CSR) of points from two or more classes (which is called the CSR independence, henceforth). New versions of overall and cell-specific tests based on NNCTs (i.e., NNCT-tests) are introduced and compared with Dixon’s overall and cell-specific tests and various other spatial clustering methods. Overall segregation tests are used to detect any deviation from the null case, while the cell-specific tests are post hoc pairwise spatial interaction tests that are applied when the overall test yields a significant result. The distributional properties of these tests are analyzed and finite sample performance of the tests are assessed by an extensive Monte Carlo simulation study. Furthermore, it is shown that the new NNCT-tests have better performance in terms of Type I error and power estimates. The methods are also applied on two real life data sets for illustrative purposes.}, number={8}, journal={Computational Statistics & Data Analysis}, publisher={Elsevier BV}, author={Ceyhan, Elvan}, year={2009}, month={Jun}, pages={2786–2808} }
 @article{ceyhan_2008, title={On the use of nearest neighbor contingency tables for testing spatial segregation}, volume={17}, ISSN={1352-8505 1573-3009}, url={http://dx.doi.org/10.1007/S10651-008-0104-X}, DOI={10.1007/S10651-008-0104-X}, abstractNote={For two or more classes (or types) of points, nearest neighbor contingency tables (NNCTs) are constructed using nearest neighbor (NN) frequencies and are used in testing spatial segregation of the classes. Pielou’s test of independence, Dixon’s cell-specific, class-specific, and overall tests are the tests based on NNCTs (i.e., they are NNCT-tests). These tests are designed and intended for use under the null pattern of random labeling (RL) of completely mapped data. However, it has been shown that Pielou’s test is not appropriate for testing segregation against the RL pattern while Dixon’s tests are. In this article, we compare Pielou’s and Dixon’s NNCT-tests; introduce the one-sided versions of Pielou’s test; extend the use of NNCT-tests for testing complete spatial randomness (CSR) of points from two or more classes (which is called CSR independence, henceforth). We assess the finite sample performance of the tests by an extensive Monte Carlo simulation study and demonstrate that Dixon’s tests are also appropriate for testing CSR independence; but Pielou’s test and the corresponding one-sided versions are liberal for testing CSR independence or RL. Furthermore, we show that Pielou’s tests are only appropriate when the NNCT is based on a random sample of (base, NN) pairs. We also prove the consistency of the tests under their appropriate null hypotheses. Moreover, we investigate the edge (or boundary) effects on the NNCT-tests and compare the buffer zone and toroidal edge correction methods for these tests. We illustrate the tests on a real life and an artificial data set.}, number={3}, journal={Environmental and Ecological Statistics}, publisher={Springer Science and Business Media LLC}, author={Ceyhan, Elvan}, year={2008}, month={Oct}, pages={247–282} }
 @article{penumetcha_jedynak_hosakere_ceyhan_botteron_ratnanather_2008, title={Segmentation of arteries in MPRAGE images of the ventral medial prefrontal cortex}, volume={32}, ISSN={0895-6111}, url={http://dx.doi.org/10.1016/j.compmedimag.2007.08.013}, DOI={10.1016/j.compmedimag.2007.08.013}, abstractNote={A method for removing arteries that appear bright with intensities similar to white matter in Magnetized Prepared Rapid Gradient Echo images of the ventral medial prefrontal cortex is described. The Fast Marching method is used to generate a curve within the artery. Then, the largest connected component is selected to segment the artery which is used to mask the image. The surface reconstructed from the masked image yielded cortical thickness maps similar to those generated by manually pruning the arteries from surfaces reconstructed from the original image. The method may be useful in masking vasculature in other cortical regions.}, number={1}, journal={Computerized Medical Imaging and Graphics}, publisher={Elsevier BV}, author={Penumetcha, N. and Jedynak, B. and Hosakere, M. and Ceyhan, E. and Botteron, K.N. and Ratnanather, J.T.}, year={2008}, month={Jan}, pages={36–43} }
 @article{ceyhan_2008, title={The distribution of the domination number of class cover catch digraphs for non-uniform one-dimensional data}, volume={308}, ISSN={0012-365X}, url={http://dx.doi.org/10.1016/j.disc.2007.10.003}, DOI={10.1016/j.disc.2007.10.003}, abstractNote={For two or more classes of points in Rd with d≥1, the class cover catch digraphs (CCCDs) can be constructed using the relative positions of the points from one class with respect to the points from one or all of the other classes. The CCCDs were introduced by Priebe et al. [C.E. Priebe, J.G. DeVinney, D.J. Marchette, On the distribution of the domination number of random class catch cover digraphs. Statistics and Probability Letters 55 (2001) 239–246] who investigated the case of two classes, X and Y. They calculated the exact (i.e., finite sample) distribution of the domination number of the CCCDs based on X points relative to Y points both of which were uniformly distributed on a bounded interval. We investigate the distribution of the domination number of the CCCDs based on data from non-uniform X points on an interval with end points from Y. Then we extend these calculations for multiple Y points on bounded intervals.}, number={23}, journal={Discrete Mathematics}, publisher={Elsevier BV}, author={Ceyhan, Elvan}, year={2008}, month={Dec}, pages={5376–5393} }
 @article{ceyhan_priebe_marchette_2007, title={A new family of random graphs for testing spatial segregation}, volume={35}, ISSN={0319-5724 1708-945X}, url={http://dx.doi.org/10.1002/cjs.5550350106}, DOI={10.1002/cjs.5550350106}, abstractNote={Abstract}, number={1}, journal={Canadian Journal of Statistics}, publisher={Wiley}, author={Ceyhan, Elvan and Priebe, Carey E. and Marchette, David J.}, year={2007}, month={Mar}, pages={27–50} }
 @article{zhi_ratnanather_ceyhan_popel_brownell_2007, title={Hypotonic swelling of salicylate-treated cochlear outer hair cells}, volume={228}, ISSN={0378-5955}, url={http://dx.doi.org/10.1016/j.heares.2007.02.007}, DOI={10.1016/j.heares.2007.02.007}, abstractNote={The outer hair cell (OHC) is a hydrostat with a low hydraulic conductivity of Pf = 3 × 10−4 cm/s across the plasma membrane (PM) and subsurface cisterna that make up the OHC’s lateral wall. The SSC is structurally and functionally a transport barrier in normal cells that is known to be disrupted by salicylate. The effect of sodium salicylate on Pf is determined from osmotic experiments in which isolated, control and salicylate-treated OHCs were exposed to hypotonic solutions in a constant flow chamber. The value of Pf = 3.5 ± 0.5 × 10−4 cm/s (mean ± s.e.m., n = 34) for salicylate-treated OHCs was not significantly different from Pf = 2.4 ± 0.3 × 10−4 cm/s (mean ± s.e.m., n = 31) for untreated OHCs (p = .3302). Thus Pf is determined by the PM and is unaffected by salicylate treatment. The ratio of longitudinal strain to radial strain εz/εc = −0.76 for salicylate-treated OHCs was significantly smaller (p = .0143) from −0.72 for untreated OHCs, and is also independent of the magnitude of the applied osmotic challenge. Salicylate-treated OHCs took longer to attain a steady-state volume which is larger than that for untreated OHCs and increased in volume by 8–15% prior to hypotonic perfusion unlike sodium α-ketoglutarate-treated OHCs. It is suggested that depolymerization of cytoskeletal proteins and/or glycogen may be responsible for the large volume increase in salicylate-treated OHCs as well as the different responses to different modes of application of the hypotonic solution.}, number={1-2}, journal={Hearing Research}, publisher={Elsevier BV}, author={Zhi, Man and Ratnanather, J. Tilak and Ceyhan, Elvan and Popel, Aleksander S. and Brownell, William E.}, year={2007}, month={Jun}, pages={95–104} }
 @article{alper_akgun_kantarci_eroglu_ceyhan_onbas_duran_okur_2006, title={Demonstration of vascular abnormalities compressing esophagus by MDCT: Special focus on dysphagia lusoria}, volume={59}, ISSN={0720-048X}, url={http://dx.doi.org/10.1016/j.ejrad.2006.01.013}, DOI={10.1016/j.ejrad.2006.01.013}, abstractNote={Dysphagia lusoria (DL) is described in the literature as difficulty in swallowing caused by vascular abnormalities. The most common cause is an aberrant right subclavian artery (SCA) which passes behind the esophagus and is also called arteria lusoria (AL). Our aim was to demonstrate the use of multidetector computed tomography (MDCT) in the diagnosis of AL, as there is no comprehensive study investigating the role of MDCT in such cases.A total of 38 consecutive patients, comprising of 23 females (61%) and 15 males (39%), who had extrinsic compression were included in the study. These patients are selected from the cases who were admitted due to their gastrointestinal symptoms, such as dysphagia, epigastric pain, chronic nausea, vomiting, etc. The mean age of patients was 40 +/- 25 years (range 15-65). Following barium esophagogram and then endoscopy performed, MDCT angiography was carried out on the same or the following few days. MDCT sections were examined to determine the following: presence of vascular abnormality; the diameter and angle of that vascular structure; and the compressed area of esophagus. Radiological findings and dysphagia scores were also compared.In each of 15 cases, there was a compression due to vascular abnormality which were all located between the esophagus and the spine. There was an esophageal compression in each of 12 cases, due to right aberrant SCA, in one case due to right superior aortic arch and in two cases due to both right aortic arch and left SCA with Kommerell's diverticulum. The mean diameter and the angle of AL were 16.4 mm and 48.8 degrees , respectively, and the mean area of pressured esophagus was 194.7 mm2. Dysphagia scores of the cases was 1 in thirteen cases and 2 in two cases. However, dysphagia scores were not correlated with these parameters.MDCT angiography is a useful diagnostic tool for evaluation of patients with dysphagia, especially caused by a vascular abnormality.}, number={1}, journal={European Journal of Radiology}, publisher={Elsevier BV}, author={Alper, Fatih and Akgun, Metin and Kantarci, Mecit and Eroglu, Atilla and Ceyhan, Elvan and Onbas, Omer and Duran, Cihan and Okur, Adnan}, year={2006}, month={Jul}, pages={82–87} }
 @article{ceyhan_priebe_wierman_2006, title={Relative density of the random r-factor proximity catch digraph for testing spatial patterns of segregation and association}, volume={50}, ISSN={0167-9473}, url={http://dx.doi.org/10.1016/j.csda.2005.03.002}, DOI={10.1016/j.csda.2005.03.002}, abstractNote={Statistical pattern classification methods based on data-random graphs were introduced recently. In this approach, a random directed graph is constructed from the data using the relative positions of the data points from various classes. Different random graphs result from different definitions of the proximity region associated with each data point and different graph statistics can be employed for data reduction. The approach used in this article is based on a parameterized family of proximity maps determining an associated family of data-random digraphs. The relative arc density of the digraph is used as the summary statistic, providing an alternative to the domination number employed previously. An important advantage of the relative arc density is that, properly re-scaled, it is a U-statistic, facilitating analytic study of its asymptotic distribution using standard U-statistic central limit theory. The approach is illustrated with an application to the testing of spatial patterns of segregation and association. Knowledge of the asymptotic distribution allows evaluation of the Pitman and Hodges–Lehmann asymptotic efficacies, and selection of the proximity map parameter to optimize efficiency. Furthermore the approach presented here also has the advantage of validity for data in any dimension.}, number={8}, journal={Computational Statistics & Data Analysis}, publisher={Elsevier BV}, author={Ceyhan, Elvan and Priebe, Carey E. and Wierman, John C.}, year={2006}, month={Apr}, pages={1925–1964} }
 @article{ceyhan_priebe_2005, title={The use of domination number of a random proximity catch digraph for testing spatial patterns of segregation and association}, volume={73}, ISSN={0167-7152}, url={http://dx.doi.org/10.1016/j.spl.2005.02.012}, DOI={10.1016/j.spl.2005.02.012}, abstractNote={Priebe et al. (2001. Statist. Prob. Lett. 55, 239–246) introduced the class cover catch digraphs and computed the distribution of the domination number of such digraphs for one-dimensional data. In higher dimensions these calculations are extremely difficult due to the geometry of the proximity regions; and only upper-bounds are available. In this article, we introduce a new type of data-random proximity map and the associated (di)graph in Rd. We find the asymptotic distribution of the domination number and use it for testing spatial point patterns of segregation and association.}, number={1}, journal={Statistics & Probability Letters}, publisher={Elsevier BV}, author={Ceyhan, Elvan and Priebe, Carey E.}, year={2005}, month={Jun}, pages={37–50} }