6,151 research outputs found
Controlling for Unobserved Confounds in Classification Using Correlational Constraints
As statistical classifiers become integrated into real-world applications, it
is important to consider not only their accuracy but also their robustness to
changes in the data distribution. In this paper, we consider the case where
there is an unobserved confounding variable that influences both the
features and the class variable . When the influence of
changes from training to testing data, we find that the classifier accuracy can
degrade rapidly. In our approach, we assume that we can predict the value of
at training time with some error. The prediction for is then fed to
Pearl's back-door adjustment to build our model. Because of the attenuation
bias caused by measurement error in , standard approaches to controlling for
are ineffective. In response, we propose a method to properly control for
the influence of by first estimating its relationship with the class
variable , then updating predictions for to match that estimated
relationship. By adjusting the influence of , we show that we can build a
model that exceeds competing baselines on accuracy as well as on robustness
over a range of confounding relationships.Comment: 9 page
PhotoRaptor - Photometric Research Application To Redshifts
Due to the necessity to evaluate photo-z for a variety of huge sky survey
data sets, it seemed important to provide the astronomical community with an
instrument able to fill this gap. Besides the problem of moving massive data
sets over the network, another critical point is that a great part of
astronomical data is stored in private archives that are not fully accessible
on line. So, in order to evaluate photo-z it is needed a desktop application
that can be downloaded and used by everyone locally, i.e. on his own personal
computer or more in general within the local intranet hosted by a data center.
The name chosen for the application is PhotoRApToR, i.e. Photometric Research
Application To Redshift (Cavuoti et al. 2015, 2014; Brescia 2014b). It embeds a
machine learning algorithm and special tools dedicated to preand
post-processing data. The ML model is the MLPQNA (Multi Layer Perceptron
trained by the Quasi Newton Algorithm), which has been revealed particularly
powerful for the photo-z calculation on the base of a spectroscopic sample
(Cavuoti et al. 2012; Brescia et al. 2013, 2014a; Biviano et al. 2013).
The PhotoRApToR program package is available, for different platforms, at the
official website (http://dame.dsf.unina.it/dame_photoz.html#photoraptor).Comment: User Manual of the PhotoRaptor tool, 54 pages. arXiv admin note:
substantial text overlap with arXiv:1501.0650
Recent Advances in Transfer Learning for Cross-Dataset Visual Recognition: A Problem-Oriented Perspective
This paper takes a problem-oriented perspective and presents a comprehensive
review of transfer learning methods, both shallow and deep, for cross-dataset
visual recognition. Specifically, it categorises the cross-dataset recognition
into seventeen problems based on a set of carefully chosen data and label
attributes. Such a problem-oriented taxonomy has allowed us to examine how
different transfer learning approaches tackle each problem and how well each
problem has been researched to date. The comprehensive problem-oriented review
of the advances in transfer learning with respect to the problem has not only
revealed the challenges in transfer learning for visual recognition, but also
the problems (e.g. eight of the seventeen problems) that have been scarcely
studied. This survey not only presents an up-to-date technical review for
researchers, but also a systematic approach and a reference for a machine
learning practitioner to categorise a real problem and to look up for a
possible solution accordingly
Automatic Labelling and Document Clustering for Forensic Analysis
In computer forensic analysis, retrieved data is in unstructured text, whose analysis by computer examiners is difficult to be performed. In proposed approach the forensic analysis is done very systematically i.e. retrieved data is in unstructured format get particular structure by using high quality well known algorithm and automatic cluster labelling method. Indexing is performed on txt, doc, and pdf file which automatically estimate the number of clusters with automatic labelling to it. In the proposed approach DBSCAN algorithm and K-mean algorithm are used; which makes it very easy to retrieve most relevant information for forensic analysis also the automated methods of analysis are of great interest. In particular, algorithms for clustering documents can facilitate the discovery of new and useful knowledge from the documents under analysis. Two methods are used for document clustering for forensic analysis; the first method uses an x2 test of significance to detect different word usage across categories in the hierarchy which is well suited for testing dependencies when count data is available. The second method selects words which both occur frequently in a cluster and effectively discriminate the given cluster from the other clusters. Finally, we also present and discuss several practical results that can be useful for researchers of forensic analysis
Facilitating High Performance Code Parallelization
With the surge of social media on one hand and the ease of obtaining information due to cheap sensing devices and open source APIs on the other hand, the amount of data that can be processed is as well vastly increasing. In addition, the world of computing has recently been witnessing a growing shift towards massively parallel distributed systems due to the increasing importance of transforming data into knowledge in today’s data-driven world. At the core of data analysis for all sorts of applications lies pattern matching. Therefore, parallelizing pattern matching algorithms should be made efficient in order to cater to this ever-increasing abundance of data. We propose a method that automatically detects a user’s single threaded function call to search for a pattern using Java’s standard regular expression library, and replaces it with our own data parallel implementation using Java bytecode injection. Our approach facilitates parallel processing on different platforms consisting of shared memory systems (using multithreading and NVIDIA GPUs) and distributed systems (using MPI and Hadoop). The major contributions of our implementation consist of reducing the execution time while at the same time being transparent to the user. In addition to that, and in the same spirit of facilitating high performance code parallelization, we present a tool that automatically generates Spark Java code from minimal user-supplied inputs. Spark has emerged as the tool of choice for efficient big data analysis. However, users still have to learn the complicated Spark API in order to write even a simple application. Our tool is easy to use, interactive and offers Spark’s native Java API performance. To the best of our knowledge and until the time of this writing, such a tool has not been yet implemented
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