Merging KK-means with hierarchical clustering for identifying general-shaped groups

Clustering partitions a dataset such that observations placed together in a group are similar but different from those in other groups. Hierarchical and $K$-means clustering are two approaches but have different strengths and weaknesses. For instance, hierarchical clustering identifies groups in a tree-like structure but suffers from computational complexity in large datasets while $K$-means clustering is efficient but designed to identify homogeneous spherically-shaped clusters. We present a hybrid non-parametric clustering approach that amalgamates the two methods to identify general-shaped clusters and that can be applied to larger datasets. Specifically, we first partition the dataset into spherical groups using $K$-means. We next merge these groups using hierarchical methods with a data-driven distance measure as a stopping criterion. Our proposal has the potential to reveal groups with general shapes and structure in a dataset. We demonstrate good performance on several simulated and real datasets.Comment: 16 pages, 1 table, 9 figures; accepted for publication in Sta

The role of heavy fermions

Heavy dynamical fermions with masses around the cut-off do not change the low energy physics apart from a finite renormalization of the gauge coupling. In this paper we study how light the heavy fermions have to be to cause more than this trivial renormalization.Comment: uuencoded 3 page postscript contribution to Lattice 93, COLO-HEP-33

Cost Sharing for Biodiversity Conservation: A Conceptual Framework

„h Many resource users undertake actions that conserve biodiversity. If, however, there were public demand for more conservation than would be provided voluntarily by the private sector alone, there are two broad principles for determining who should bear the costs ¡X ¡¥impacter pays¡¦ or ¡¥beneficiary pays¡¦. The two principles have different efficiency and distributional effects. „h A fundamental step in determining which cost sharing principle to apply is the clarification of the rights and responsibilities implied by existing property rights. This is an important issue that requires further work. „h If property rights effectively require resource users to meet an environmental standard, resource users who fail to achieve this may be considered to generate external costs. In these circumstances, on efficiency grounds, the impacter pays principle should generally be adopted to internalise external costs. This effectively amounts to enforcement of an individual¡¦s existing legal responsibilities. However, if the costs of implementing the impacter pays principle were to outweigh its efficiency advantages, the beneficiary pays principle may be considered.environment, conservation, biodiversity

A separability index for clustering and classification problems with applications to cluster merging and systematic evaluation of clustering algorithms

A separability index quantifying the degree of difficulty in a hard clustering problem is proposed under assumptions of a multivariate Gaussian distribution for each group. We first define a preliminary index and explore its properties both theoretically and numerically. Adjustments are then made to this index so that the final refinement is also interpretable in terms of the Adjusted Rand Index between a true grouping and its hypothetical idealized clustering, taken as a surrogate of clustering complexity. Our derived index is used to develop a data-simulation algorithm that generates samples according to the prescribed value of the index. This algorithm is particularly useful for systematically generating datasets with varying degrees of clustering difficulty which we use to evaluate performance of different clustering algorithms. The index is also shown to be useful in providing a summary of the distinctiveness of classes in grouped datasets

Vikings across the Atlantic: Emigration and the Building of a Greater Norway, 1860-1945

Review of: "Vikings across the Atlantic: Emigration and the Building of a Greater Norway, 1860-1945," by Anna M. Peterson

Comorbidity of Attention Deficit Hyperactivity Disorder and gender with internalizing and externalizing symptoms.

This study examined the association between internalizing and externalizing symptoms, gender, and the diagnosis of Attention-Deficit/Hyperactivity Disorder. Participants included 104 males and 74 females, aged 6 to 16 from a diagnostic clinic. Parents and teachers completed the Attention Deficit Disorders Evaluation Scale, Second Edition (ADDES-2) to determine whether they met the criteria for Attention-Deficit/Hyperactivity Disorder and the Behavior Assessment System for Children (BASC) in order to measure internalizing and externalizing symptoms. Regression analyses indicated partial support for association between inattention and internalizing symptoms, with higher ratings of inattention found for both anxiety and depression as rated by parents and higher ratings of inattention for depression as rated by school. Although not predicted, a positive association was also found between home and school rated hyperactivity and depression. As hypothesized, higher ratings of hyperactivity in the home environment were predictive of all three externalizing behaviors as rated by parents, including measures of aggression, hyperactivity, and conduct problems, but only teacher ratings of hyperactivity. In addition, hyperactivity in the school environment was predictive of all teacher ratings of aggression, hyperactivity and conduct problems and only aggression as rated by parents. All parent and teacher ratings of externalizing behaviors showed significantly higher scores for males. On measures of internalizing symptoms, no significant relationships were found with gender and parent and teacher ratings on inattention and hyperactivity, other than in the area of teacher ratings of somatization. These results have important implications in terms of identification, treatment, and long-term outcomes of affected individuals