43,998 research outputs found
Bayesian Hierarchical Modelling for Tailoring Metric Thresholds
Software is highly contextual. While there are cross-cutting `global'
lessons, individual software projects exhibit many `local' properties. This
data heterogeneity makes drawing local conclusions from global data dangerous.
A key research challenge is to construct locally accurate prediction models
that are informed by global characteristics and data volumes. Previous work has
tackled this problem using clustering and transfer learning approaches, which
identify locally similar characteristics. This paper applies a simpler approach
known as Bayesian hierarchical modeling. We show that hierarchical modeling
supports cross-project comparisons, while preserving local context. To
demonstrate the approach, we conduct a conceptual replication of an existing
study on setting software metrics thresholds. Our emerging results show our
hierarchical model reduces model prediction error compared to a global approach
by up to 50%.Comment: Short paper, published at MSR '18: 15th International Conference on
Mining Software Repositories May 28--29, 2018, Gothenburg, Swede
Nonparametric Hierarchical Clustering of Functional Data
In this paper, we deal with the problem of curves clustering. We propose a
nonparametric method which partitions the curves into clusters and discretizes
the dimensions of the curve points into intervals. The cross-product of these
partitions forms a data-grid which is obtained using a Bayesian model selection
approach while making no assumptions regarding the curves. Finally, a
post-processing technique, aiming at reducing the number of clusters in order
to improve the interpretability of the clustering, is proposed. It consists in
optimally merging the clusters step by step, which corresponds to an
agglomerative hierarchical classification whose dissimilarity measure is the
variation of the criterion. Interestingly this measure is none other than the
sum of the Kullback-Leibler divergences between clusters distributions before
and after the merges. The practical interest of the approach for functional
data exploratory analysis is presented and compared with an alternative
approach on an artificial and a real world data set
Modeling and visualizing uncertainty in gene expression clusters using Dirichlet process mixtures
Although the use of clustering methods has rapidly become one of the standard computational approaches in the literature of microarray gene expression data, little attention has been paid to uncertainty in the results obtained. Dirichlet process mixture (DPM) models provide a nonparametric Bayesian alternative to the bootstrap approach to modeling uncertainty in gene expression clustering. Most previously published applications of Bayesian model-based clustering methods have been to short time series data. In this paper, we present a case study of the application of nonparametric Bayesian clustering methods to the clustering of high-dimensional nontime series gene expression data using full Gaussian covariances. We use the probability that two genes belong to the same cluster in a DPM model as a measure of the similarity of these gene expression profiles. Conversely, this probability can be used to define a dissimilarity measure, which, for the purposes of visualization, can be input to one of the standard linkage algorithms used for hierarchical clustering. Biologically plausible results are obtained from the Rosetta compendium of expression profiles which extend previously published cluster analyses of this data
Extracting Hierarchies of Search Tasks & Subtasks via a Bayesian Nonparametric Approach
A significant amount of search queries originate from some real world
information need or tasks. In order to improve the search experience of the end
users, it is important to have accurate representations of tasks. As a result,
significant amount of research has been devoted to extracting proper
representations of tasks in order to enable search systems to help users
complete their tasks, as well as providing the end user with better query
suggestions, for better recommendations, for satisfaction prediction, and for
improved personalization in terms of tasks. Most existing task extraction
methodologies focus on representing tasks as flat structures. However, tasks
often tend to have multiple subtasks associated with them and a more
naturalistic representation of tasks would be in terms of a hierarchy, where
each task can be composed of multiple (sub)tasks. To this end, we propose an
efficient Bayesian nonparametric model for extracting hierarchies of such tasks
\& subtasks. We evaluate our method based on real world query log data both
through quantitative and crowdsourced experiments and highlight the importance
of considering task/subtask hierarchies.Comment: 10 pages. Accepted at SIGIR 2017 as a full pape
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