scholarly journals The Q-matrix completion problem

Author(s):  
Luz DeAlba, ◽  
Leslie Hogben ◽  
Bhaba Sarma
2015 ◽  
Vol 07 (04) ◽  
pp. 1550052 ◽  
Author(s):  
Bhaba Kumar Sarma ◽  
Kalyan Sinha

A real [Formula: see text] matrix is a [Formula: see text]-matrix if for [Formula: see text] the sum of all [Formula: see text] principal minors is positive. A digraph [Formula: see text] is said to have positive [Formula: see text]-completion if every partial positive [Formula: see text]-matrix specifying [Formula: see text] can be completed to a positive [Formula: see text]-matrix. In this paper, necessary conditions for a digraph to have positive [Formula: see text]-completion are obtained and sufficient conditions for a digraph to have positive [Formula: see text]-completion are provided. The digraphs of order at most 4 that include all loops and have positive [Formula: see text]-completion are characterized. Tournaments whose complements have positive [Formula: see text]-completion are singled out. Further, some comparisons between the [Formula: see text]-matrix and positive [Formula: see text]-matrix completion problems have been made.


2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Kalyan Sinha

A matrix is a Q0-matrix if for every k∈{1,2,…,n}, the sum of all k×k principal minors is nonnegative. In this paper, we study some necessary and sufficient conditions for a digraph to have Q0-completion. Later on we discuss the relationship between Q and Q0-matrix completion problem. Finally, a classification of the digraphs of order up to four is done based on Q0-completion.


Author(s):  
Wenqing Li ◽  
Chuhan Yang ◽  
Saif Eddin Jabari

This paper addresses the problem of short-term traffic prediction for signalized traffic operations management. Specifically, we focus on predicting sensor states in high-resolution (second-by-second). This contrasts with traditional traffic forecasting problems, which have focused on predicting aggregated traffic variables, typically over intervals that are no shorter than five minutes. Our contributions can be summarized as offering three insights: first, we show how the prediction problem can be modeled as a matrix completion problem. Second, we use a block-coordinate descent algorithm and demonstrate that the algorithm converges in sublinear time to a block coordinate-wise optimizer. This allows us to capitalize on the “bigness” of high-resolution data in a computationally feasible way. Third, we develop an ensemble learning (or adaptive boosting) approach to reduce the training error to within any arbitrary error threshold. The latter uses past days so that the boosting can be interpreted as capturing periodic patterns in the data. The performance of the proposed method is analyzed theoretically and tested empirically using both simulated data and a real-world high-resolution traffic data set from Abu Dhabi, United Arab Emirates. Our experimental results show that the proposed method outperforms other state-of-the-art algorithms.


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