From sekhar.tatikonda at yale.edu Wed Aug 15 09:10:26 2018 From: sekhar.tatikonda at yale.edu (Sekhar Tatikonda) Date: Wed, 15 Aug 2018 09:10:26 -0400 Subject: [YPNG] YPNG Friday 17 August, 11:00--1:00 Message-ID: Hi Folks, This Friday Chris Harshaw will talk about: "Submodularity Beyond Lattices: Matrices, Polynomials, Arbitrary Real Vector Spaces - Oh My!" In the recent YPNG seminars, we've heard about submodular set functions and their "continuous" counterparts defined on Rn. In both discrete and continuous domains, these submodular functions are characterized by a diminishing returns condition and admit efficient maximization algorithms. However, the definitions of these functions heavily relied on an underlying lattice structure in the domain. For many domains, such as matrices, polynomials, and function spaces, we can envision a notion of diminishing returns, although there is not a clear choice of lattice. In this talk, we introduce a broader notion of submodularity that extends to arbitrary real vector spaces. We also give approximation algorithms for maximizing these nonconvex objectives. Finally, we discuss potential applications in maximum likelihood estimation. See you Friday at 11. Regards, sekhar -------------- next part -------------- An HTML attachment was scrubbed... URL: From sekhar.tatikonda at yale.edu Mon Aug 20 14:45:02 2018 From: sekhar.tatikonda at yale.edu (Sekhar Tatikonda) Date: Mon, 20 Aug 2018 14:45:02 -0400 Subject: [YPNG] YPNG Friday 24 August, 11:00--1:00 Message-ID: Hi Folks, This Friday Derek Feng will present: "Testing for Balance in Social Networks" Friendship and antipathy exist in concert with one another in real social networks. Despite the role they play in social interactions, antagonistic ties are poorly understood and infrequently measured. One important theory of negative ties that has received relatively little empirical evaluation is balance theory, the codification of the adage `the enemy of my enemy is my friend' and similar sayings. Unbalanced triangles are those with an odd number of negative ties, and the theory posits that such triangles are rare. To test for balance, previous works have utilized a permutation test on the edge signs. The flaw in this method, however, is that it assumes that negative and positive edges are interchangeable. In reality, they could not be more different. Here, we propose a novel test of balance that accounts for this discrepancy and show that our test is more accurate at detecting balance. Along the way, we prove asymptotic normality of the test statistic under our null model, which is of independent interest. Our case study is a novel dataset of signed networks we collected from 32 isolated, rural villages in Honduras. Contrary to previous results, we find that there is only marginal evidence for balance in social tie formation in this setting. See you Friday at 11 in the Stat's classroom. Regards, Sekhar -------------- next part -------------- An HTML attachment was scrubbed... URL: From sekhar.tatikonda at yale.edu Tue Aug 21 08:24:43 2018 From: sekhar.tatikonda at yale.edu (Sekhar Tatikonda) Date: Tue, 21 Aug 2018 08:24:43 -0400 Subject: [YPNG] YPNG Friday 24 August, 11:00--1:00 -- NEW ROOM LOCATION Message-ID: Hi Folks, Room change: the YPNG seminar this Friday will be held in 205 LOM (12 Hillhouse) at the same time 11-1. The Stat's classroom is being used for the new student placement exam. Regards, sekhar On Mon, Aug 20, 2018 at 2:45 PM, Sekhar Tatikonda wrote: > > Hi Folks, > > This Friday Derek Feng will present: > > "Testing for Balance in Social Networks" > > Friendship and antipathy exist in concert with one another in real social > networks. Despite the role they play in social interactions, antagonistic > ties are poorly understood and infrequently measured. One important theory > of negative ties that has received relatively little empirical evaluation > is balance theory, the codification of the adage `the enemy of my enemy is > my friend' and similar sayings. Unbalanced triangles are those with an odd > number of negative ties, and the theory posits that such triangles are > rare. To test for balance, previous works have utilized a permutation test > on the edge signs. The flaw in this method, however, is that it assumes > that negative and positive edges are interchangeable. In reality, they > could not be more different. Here, we propose a novel test of balance that > accounts for this discrepancy and show that our test is more accurate at > detecting balance. Along the way, we prove asymptotic normality of the test > statistic under our null model, which is of independent interest. Our case > study is a novel dataset of signed networks we collected from 32 isolated, > rural villages in Honduras. Contrary to previous results, we find that > there is only marginal evidence for balance in social tie formation in this > setting. > > See you Friday at 11 in the Stat's classroom. > > Regards, > Sekhar > > > -------------- next part -------------- An HTML attachment was scrubbed... URL: