Mostrando recursos 1 - 7 de 7

  1. A tm Plug-In for Distributed Text Mining in R

    Theußl, Stefan; Feinerer, Ingo; Hornik, Kurt
    R has gained explicit text mining support with the tm package enabling statisticians to answer many interesting research questions via statistical analysis or modeling of (text) corpora. However, we typically face two challenges when analyzing large corpora: (1) the amount of data to be processed in a single machine is usually limited by the available main memory (i.e., RAM), and (2) the more data to be analyzed the higher the need for efficient procedures for calculating valuable results. Fortunately, adequate programming models like MapReduce facilitate parallelization of text mining tasks and allow for processing data sets beyond what would fit into memory by using a distributed file...

  2. A tm Plug-In for Distributed Text Mining in R

    Theußl, Stefan; Feinerer, Ingo; Hornik, Kurt
    R has gained explicit text mining support with the tm package enabling statisticians to answer many interesting research questions via statistical analysis or modeling of (text) corpora. However, we typically face two challenges when analyzing large corpora: (1) the amount of data to be processed in a single machine is usually limited by the available main memory (i.e., RAM), and (2) the more data to be analyzed the higher the need for efficient procedures for calculating valuable results. Fortunately, adequate programming models like MapReduce facilitate parallelization of text mining tasks and allow for processing data sets beyond what would fit into memory by using a distributed file...

  3. SEARCH Project Delphi

    Sinozic, Tanja
    This paper describes a plan to implement the Delphi method to obtain consensus of expert opinions on policy statements derived from research evidence. The evidence is based on a three-year large-scale European Union (EU) research project ("SEARCH"). The SEARCH project focuses on trade, migration, innovation and institutional issues on relationships between the European Union (EU) and its neighbouring countries (NCs). The main objective of the use of Delphi in this context is to obtain as many high-quality responses and opinions as possible on policy implications of SEARCH project results. The SEARCH Project Delphi aims to inform policy formulation at the EU level, specifically European Neighbourhood Policy (ENP). (author's...

  4. Modelling Primary Energy Consumption under Model Uncertainty

    Csereklyei, Zsuzsanna; Humer, Stefan
    This paper examines the long-term relationship between primary energy consumption and other key macroeconomic variables, including real GDP, labour force, capital stock and technology, using a panel dataset for 64 countries over the period 1965-2009. Deploying panel error correction models, we find that there is a positive relationship running from physical capital, GDP, and population to primary energy consumption. We observe however a negative relationship between total factor productivity and primary energy usage. Significant differences arise in the magnitude of the cointegration coefficients, when we allow for differences in geopolitics and wealth levels. We also argue that inference on the...

  5. The covariance structure of conditional maximum likelihood estimates

    Strasser, Helmut
    In this paper we consider conditional maximum likelihood (cml) estimates for item parameters in the Rasch model under random subject parameters. We give a simple approximation for the asymptotic covariance matrix of the cml-estimates. The approximation is stated as a limit theorem when the number of item parameters goes to infinity. The results contain precise mathematical information on the order of approximation. The results enable the analysis of the covariance structure of cml-estimates when the number of items is large. Let us give a rough picture. The covariance matrix has a dominating main diagonal containing the asymptotic variances of the estimators. These variances are almost equal to the efficient...

  6. Asymptotic expansions for conditional moments of Bernoulli trials

    Strasser, Helmut
    In this paper we study conditional distributions of independent, but not identically distributed Bernoulli random variables. The conditioning variable is the sum of the Bernoulli variables. We obtain Edgeworth expansions for the conditional expectations and the conditional variances and covariances. The results are of basic interest for several applications, e.g. for the study of conditional maximum likelihood estimation in Rasch models with many item parameters.

  7. Business Cycle Synchronization During US Recessions Since the Beginning of the 1870s

    Antonakakis, Nikolaos
    This paper examines the synchronization of business cycles across the G7 countries during US recessions since the 1870s. Using a dynamic measure of correlations, results depend on the globalization period under consideration. During the 2007-2009 recession, business cycles co-movements increased to unprecedented levels. (author's abstract)

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