Shrinkage and variable selection by polytopes

Constrained estimators that enforce variable selection and grouping of highly correlated data have been shown to be successful in finding sparse representations and obtaining good performance in prediction. We consider polytopes as a general class of compact and convex constraint regions. Well-established procedures like LASSO (Tibshirani, 1996) or OSCAR (Bondell and Reich, 2008) are shown to be based on specific subclasses of polytopes. The general framework of polytopes can be used to investigate the geometric structure that underlies these procedures. Moreover, we propose a specifically designed class of polytopes that enforces variable selection and grouping. Simulation studies and an application illustrate the usefulness of the proposed method.     

决策的约束及有效决策的制度安排

决策面临决策问题选择、决策项目分析和可行方案搜寻等三个约束,任何方面的缺失都导致决策失当。决策者本身的因素、外部对决策者的影响对决策次序和议事日程产生影响,组织结构化形成知识层级进而影响组织知识、组织内决策博弈和治理结构等因素决定决策分析的效果,方案集的“关闭”损害了方案集的完备性,直接决定了方案的性质以及选择。有效的决策需要社会资本的支持,需要决策制度保障。     

西部地区的区域发展与生态环境的制约——以甘肃省两西地区为例

本文分析了甘肃省两西地区的发展现状以及进一步发展的环境制约,提出类似甘肃省两西地区这样的西部地区,区域的发展必须要从长计议,最终要实现可持续发展.