12,921 research outputs found
Switching Regression Models and Causal Inference in the Presence of Discrete Latent Variables
Given a response and a vector of predictors,
we investigate the problem of inferring direct causes of among the vector
. Models for that use all of its causal covariates as predictors enjoy
the property of being invariant across different environments or interventional
settings. Given data from such environments, this property has been exploited
for causal discovery. Here, we extend this inference principle to situations in
which some (discrete-valued) direct causes of are unobserved. Such cases
naturally give rise to switching regression models. We provide sufficient
conditions for the existence, consistency and asymptotic normality of the MLE
in linear switching regression models with Gaussian noise, and construct a test
for the equality of such models. These results allow us to prove that the
proposed causal discovery method obtains asymptotic false discovery control
under mild conditions. We provide an algorithm, make available code, and test
our method on simulated data. It is robust against model violations and
outperforms state-of-the-art approaches. We further apply our method to a real
data set, where we show that it does not only output causal predictors, but
also a process-based clustering of data points, which could be of additional
interest to practitioners.Comment: 46 pages, 14 figures; real-world application added in Section 5.2;
additional numerical experiments added in the Appendix
Recent advances in directional statistics
Mainstream statistical methodology is generally applicable to data observed
in Euclidean space. There are, however, numerous contexts of considerable
scientific interest in which the natural supports for the data under
consideration are Riemannian manifolds like the unit circle, torus, sphere and
their extensions. Typically, such data can be represented using one or more
directions, and directional statistics is the branch of statistics that deals
with their analysis. In this paper we provide a review of the many recent
developments in the field since the publication of Mardia and Jupp (1999),
still the most comprehensive text on directional statistics. Many of those
developments have been stimulated by interesting applications in fields as
diverse as astronomy, medicine, genetics, neurology, aeronautics, acoustics,
image analysis, text mining, environmetrics, and machine learning. We begin by
considering developments for the exploratory analysis of directional data
before progressing to distributional models, general approaches to inference,
hypothesis testing, regression, nonparametric curve estimation, methods for
dimension reduction, classification and clustering, and the modelling of time
series, spatial and spatio-temporal data. An overview of currently available
software for analysing directional data is also provided, and potential future
developments discussed.Comment: 61 page
Small-variance asymptotics for Bayesian neural networks
Bayesian neural networks (BNNs) are a rich and flexible class of models that have several advantages over standard feedforward networks, but are typically expensive to train on large-scale data. In this thesis, we explore the use of small-variance asymptotics-an approach to yielding fast algorithms from probabilistic models-on various Bayesian neural network models. We first demonstrate how small-variance asymptotics shows precise connections between standard neural networks and BNNs; for example, particular sampling algorithms for BNNs reduce to standard backpropagation in the small-variance limit. We then explore a more complex BNN where the number of hidden units is additionally treated as a random variable in the model. While standard sampling schemes would be too slow to be practical, our asymptotic approach yields a simple method for extending standard backpropagation to the case where the number of hidden units is not fixed. We show on several data sets that the resulting algorithm has benefits over backpropagation on networks with a fixed architecture.2019-01-02T00:00:00
Using Markov Models and Statistics to Learn, Extract, Fuse, and Detect Patterns in Raw Data
Many systems are partially stochastic in nature. We have derived data driven
approaches for extracting stochastic state machines (Markov models) directly
from observed data. This chapter provides an overview of our approach with
numerous practical applications. We have used this approach for inferring
shipping patterns, exploiting computer system side-channel information, and
detecting botnet activities. For contrast, we include a related data-driven
statistical inferencing approach that detects and localizes radiation sources.Comment: Accepted by 2017 International Symposium on Sensor Networks, Systems
and Securit
Asymptotic equivalence for inhomogeneous jump diffusion processes and white noise
We prove the global asymptotic equivalence between the experiments generated
by the discrete (high frequency) or continuous observation of a path of a time
inhomogeneous jump-diffusion process and a Gaussian white noise experiment.
Here, the considered parameter is the drift function, and we suppose that the
observation time tends to . The approximation is given in the sense
of the Le Cam -distance, under smoothness conditions on the unknown
drift function. These asymptotic equivalences are established by constructing
explicit Markov kernels that can be used to reproduce one experiment from the
other.Comment: 20 pages; to appear on ESAIM: P\&S. In this version there are some
improvements in the exposition following the reports suggestion
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