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Analysis of spatio-temporal mobile phone data: a case study in the metropolitan area of Milan
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Get PDFBagging Voronoi classifiers for clustering spatial functional data
No full textWe propose a bagging strategy based on random Voronoi tessellations for the exploration of geo- referenced functional data, suitable for different purposes (e.g., classification, regression, dimensional reduction, ...). Urged by an application to environmental data contained in the Surface Solar Energy database, we focus in particular on the problem of clustering functional data indexed by the sites of a spatial finite lattice. We thus illustrate our strategy by implementing a specific algorithm whose rationale is to (i) replace the original data set with a reduced one, composed by local representatives of neighbor- hoods covering the entire investigated area; (ii) analyze the local representatives; (iii) repeat the previous analysis many times for different reduced data sets associated to randomly generated different sets of neighborhoods, thus obtaining many different weak formulations of the analysis; (iv) finally, bag together the weak analyses to obtain a conclusive strong analysis. Through an extensive simulation study, we show that this new procedure – which does not require an explicit model for spatial dependence – is statistically and computationally efficient
Functional clustering and alignment methods with applications
No full textWe consider the issue of classification of functional data and, in particular, we deal with the problem of curve clustering when curves are misaligned.
In the proposed setting, we aim at jointly aligning and clustering the curves, via the solution of an optimization problem. We describe an iterative procedure for the solution of the optimization problem, and we detail two alternative specifications of the procedure, a k-mean version and a k-medoid version. We illustrate via applications to real data the robustness of the alignment and clustering procedure under the different specifications
Statistical models for hazard functions: a casestudy of hospitalizations in health failuretelemonitoring
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