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A VARIABLE-DIMENSION HOMOTOPY ON networkS FOR COMPUTING LINEAR SPATIAL EQUILIBRIA

DISCRETE APPLIED MATHEMATICS 1986年第2-3期13卷 131-156页

作者： JONES, PC SAIGAL, R SCHNEIDER, MH PRINCETON UNIV DEPT CIVIL ENGNPRINCETONNJ 08544

This paper presents a variable-dimension homotopy algorithm that exploits dominant market structure for computing spatial market equilibria. The algorithm is implemented on the problem's underlying network. The computational results indicate that the algorithm performs most of its work in lower dimensions and can process large problems effectively.

关键词： network algorithm complementarity spatial equilibria homotopy variable dimension

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IMPROVED TIME-BOUNDS FOR THE MAXIMUM FLOW PROBLEM: 收藏
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引用; SIAM JOURNAL ON COMPUTING 1989年第5期18卷 939-954页; 作者： AHUJA, RK ORLIN, JB TARJAN, RE PRINCETON UNIV DEPT COMP SCIPRINCETONNJ 08544 AT&T BELL LABS MURRAY HILLNJ 07974; Recently, Goldberg proposed a new approach to the maximum network flow problem. The approach yields a very simple algorithm running in O(n3)<span style="display: inline-bloc; Recently, Goldberg proposed a new approach to the maximum network flow problem. The approach yields a very simple algorithm running in $O (n^{3})$; 来源：评论; 学校读者我要写书评

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An efficient algorithm for the exact test on unordered 2 x J contingency tables with equal column sums

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COMPUTATIONAL STATISTICS & DATA ANALYSIS 1997年第3期25卷 273-285页

作者： Shao, XM UNIV CALIF LOS ANGELES DEPT PHYSIOL SCI SYST NEUROBIOL LAB LOS ANGELES CA 90095 USA

An efficient algorithm for Fisher's exact test on unordered 2 x J contingency tables is proposed based on the network algorithm described by Mehta and Patel (1980, 1983). When either all or some of the column sums are equal, this method substantially reduces the computational effort needed to obtain the exact p-value. The principal computational efficiency is gained from the idea that the network size could be reduced by multiplying the probabilities of equivalent tables in which the first row entries are permutation of each other rather than creating them repeatedly and summing up their probabilities. The ranges of the nodes in the network and the ranges of the arcs emanating from each node to the nodes at the succeeding stages are redefined, so that the algorithm creates only the representatives of equivalent tables which are permutationally distinct without missing any possible table. An equation to calculate the numbers of equivalent tables is given. This method is also applicable to exact Pearson chi-squared and exact likelihood ratio tests. Some numerical examples are presented to compare the computational time of the improved algorithm with the original network algorithm. (C) 1997 Elsevier Science B.V.

关键词： Fisher's exact test 2 x J contingency table network algorithm

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The arctic mouse-ear in Scotland - and why it is not arctic

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PLANT ECOLOGY & DIVERSITY 2008年第2期1卷 321-327页

作者： Brysting, Anne K. Univ Oslo Dept Biol Ctr Ecol & Evolutionary Synth Oslo Norway

Background: The arctic mouse-ear (Cerastium nigrescens, Caryophyllaceae) growing in the Scottish Highlands has a turbulent taxonomic (and nomenclatural) history, probably reflecting the complex allopolyploid origin of this high-polyploid species. It belongs to an intricate arctic-alpine species group (the C. alpinum complex) which has a reticulate evolutionary history formed through repeated hybridisation and polyploidisation events. Aims: In this paper, the position of the Scottish plant is discussed in the light of recently published sequence data from the whole complex. Methods: Sequences of a low-copy number nuclear gene (RPB2) of a few Scottish plants were obtained and compared to previously obtained sequences of C. nigrescens from other geographical areas, other closely related high-polyploid species as well as possible tetraploid progenitor taxa. Main findings: A network produced from the RPB2 sequences clearly showed that the dodecaploid plant growing in the Scottish Highlands has a common origin with C. nigrescens from Scandinavia and Shetland. By using the same approach, it was also possible to identify hybrids among Scottish plants resulting from interploidal crosses between C. alpinum (8x) and C. nigrescens (12x). Such hybrids possessed a combination of RPB2 sequences from these two parental species. Conclusions: The Scottish C. nigrescens shares its evolutionary history with C. nigrescens from Shetland and mainland Norway, and this non-arctic taxon is clearly separated from the artic taxon, C. arcticum, with which it has previously been considered conspecific.

关键词： allopolyploidy interploidal gene flow low-copy nuclear region network algorithm

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The automated malnutrition assessment

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NUTRITION 2013年第1期29卷 113-121页

作者： David, Gil Bernstein, Larry Howard Coifman, Ronald R. Yale Univ Dept Math Program Appl Math New Haven CT 06520 USA New York Methodist Hosp Cornell Weill New York NY USA

Objective: We propose an automated nutritional assessment algorithm that provides a method for malnutrition risk prediction with high accuracy and reliability. Methods: The database used for this study was a file of 432 patients, where each patient was described by 4 laboratory parameters and 11 clinical parameters. A malnutrition risk assessment of low (1), moderate (2), or high (3) was assigned by a dietitian for each patient. An algorithm for data organization and classification using characteristic metrics for each patient was developed. For each patient, the algorithm characterized the patients' unique profile and built a characteristic metric to identify similar patients who were mapped into a classification. For each patient, the algorithm characterized the patients' classification. Results: The algorithm assigned a malnutrition risk level for different training sizes that were taken from the data. Our method resulted in average errors (distance between the automated score and the real score) of 0.386, 0.3507, 0.3454, 0.34, and 0.2907 for the 10%, 30%, 50%, 70%, and 90% training sizes, respectively. Our method outperformed the compared method even when our method used a smaller training set than the compared method. In addition, we showed that the laboratory parameters themselves were sufficient for the automated risk prediction and organized the patients into clusters that corresponded to low-, low-moderate-, moderate-, moderate-high-, and high-risk areas. The organization and visualization methods provided a tool for the exploration and navigation of the data points. Conclusion: The problem of rapidly identifying risk and severity of malnutrition is crucial for minimizing medical and surgical complications. These are not easily performed or adequately expedited. We characterized for each patient a unique profile and mapped similar patients into a classification. We also found that the laboratory parameters were sufficient for the automated risk prediction.

关键词： network algorithm Unsupervised classification Malnutrition screening Protein-energy malnutrition Malnutrition risk Characteristic metric Characteristic profile Data characterization Non-linear differential diagnosis

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A HYBRID algorithm FOR FISHERS EXACT TEST IN UNORDERED RXC CONTINGENCY-TABLES

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COMMUNICATIONS IN STATISTICS-THEORY AND METHODS 1986年第2期15卷 387-403页

作者： MEHTA, CR PATEL, NR HARVARD UNIV SCH MEDDANA FARBER CANC INSTDEPT BIOSTATBOSTONMA 02115 INDIAN INST MANAGEMENT AHMEDABAD 380015GUJARATINDIA

I hybrid significance test, which blends exact and asymptotic theory in a unique way, is presided as an alternative to Fisher's exact test for unordered rxc contingency tables. The hybrid test is almost equivlent to Fisher's exact test, but requires considerably less computational effort The accuracy of the hybrid p-value is not compromised by sparse contingency tables.

关键词： Fisher's exact test unordered aontingene tables network algorithm hybrid algorithm sparse aontingene tables permutation distribution exact tests nonparametrio inference implicit enumeration

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Railway timetabling: a maximum bottleneck path algorithm for finding an additional train path

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PUBLIC TRANSPORT 2021年第3期13卷 597-623页

作者： Ljunggren, Fredrik Persson, Kristian Peterson, Anders Schmidt, Christiane Linkoping Univ Commun & Transport Syst ITN Norrkoping Sweden Trafikverket Stockholm Sweden Sweco Stockholm Sweden

We present an algorithm to insert a train path in an existing railway timetable close to operation, when we want to affect the existing (passenger) traffic as little as possible. Thus, we consider all other trains as fixed, and aim for a resulting train path that maximizes the bottleneck robustness, that is, a train path that maximizes the temporal distance to neighboring trains in the timetable. Our algorithm is based on a graph formulation of the problem and uses a variant of Dijkstra's algorithm. We present an extensive experimental evaluation of our algorithm for the Swedish railway stretch from Malmo to Hallsberg. Moreover, we analyze the size of our constructed graph.

关键词： Railway timetabling Robust train path Bottleneck train path network algorithm Freight transportation

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Exact family-based association tests for biallelic data

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GENETIC EPIDEMIOLOGY 2005年第3期29卷 185-194页

作者： Schneiter, K Laird, N Corcoran, C Harvard Univ Sch Publ Hlth Dept Biostat Boston MA 02115 USA Utah State Univ Dept Math & Stat Logan UT 84322 USA

Family-based study designs have an important role in the search for association between disease phenotypes and genetic markers. Unlike traditional case-control methods, family-based tests use within-family data to avoid identification of spurious associations that may result from population admixture. Many family-based association tests have been proposed to accommodate a variety of ascertainment schemes and patterns of missing data. In this report, we describe exact family-based association tests for biallelic data. Specifically, we discuss test of the null hypotheses "no linkage and no association" and "linkage, but no association". These tests, which are valid under various models for inheritance and patterns of missingness, utilize the procedure proposed by Rabinowitz and Laird [2000: Hum Hered 50:211-223] that provides a unified framework for family based association testing (FBAT). The conditioning approach implemented in FBAT makes an exact test conceptually straightforward, but computationally difficult since the minimum sufficient statistics upon which we condition do not have a conventional form. An exact test may be especially critical when accurate computation of the extreme area of the FBAT statistic is needed, such as when the study design necessitates multiple comparisons adjustments. We describe the exact approach as a useful alternative to the aymptotic test and show that the exact tests for biallelic data may be most useful for the recessive disease model.

关键词： linkage genetic association network algorithm

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GENERATING STRUCTURE SPECIFIC networkS

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ADVANCES IN COMPLEX SYSTEMS 2010年第2期13卷 239-250页

作者： Hakansson, N. Jonsson, A. Lennartsson, J. Lindstrom, T. Wennergren, U. Skovde Univ Syst Biol Res Ctr S-54128 Skovde Sweden Linkoping Univ IFM Therory & Modeling S-58183 Linkoping Sweden

Theoretical exploration of network structure significance requires a range of different networks for comparison. Here, we present a new method to construct networks in a spatial setting that uses spectral methods in combination with a probability distribution function. Nearly all previous algorithms for network construction have assumed randomized distribution of links or a distribution dependent on the degree of the nodes. We relax those assumptions. Our algorithm is capable of creating spectral networks along a gradient from random to highly clustered or diverse networks. Number of nodes and link density are specified from start and the structure is tuned by three parameters (gamma, sigma, kappa). The structure is measured by fragmentation, degree assortativity, clustering and group betweenness of the networks. The parameter gamma regulates the aggregation in the spatial node pattern and sigma and kappa regulates the probability of link forming.

关键词： network spectral assortativity fragmentation clustering betweenness centralization spatial network network algorithm

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Updating exact P-values for the conditional likelihood ratio test of independence

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JOURNAL OF STATISTICAL COMPUTATION AND SIMULATION 1999年第3期63卷 201-215页

作者： Kang, SH Klotz, JH Univ Wisconsin Madison WI USA

We consider the exact likelihood ratio test of independence conditioned on row and column margins in an r x c contingency table with multinomial sampling. We develop an update algorithm to compute the exact P-value of the test and show it is better than the network algorithm in terms of computing speed. In the algorithm the P-value is reduced to a sum of probabilities for 2 x 2 contingency tables, which we compute using the hypergeometric distribution. The same algorithm can also be used for testing homogeneity of independent multinomial populations.

关键词： exact test network algorithm multivariate hypergeometric distribution homogeneity two way contingency table

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