Outlier Detection Using Nonconvex Penalized Regression

This paper studies the outlier detection problem from the point of view of penalized regressions. Our regression model adds one mean shift parameter for each of the $n$ data points. We then apply a regularization favoring a sparse vector of mean shift parameters. The usual $L_1$ penalty yields a convex criterion, but we find that it fails to deliver a robust estimator. The $L_1$ penalty corresponds to soft thresholding. We introduce a thresholding (denoted by $\Theta$) based iterative procedure for outlier detection ($\Theta$-IPOD). A version based on hard thresholding correctly identifies outliers on some hard test problems. We find that $\Theta$-IPOD is much faster than iteratively reweighted least squares for large data because each iteration costs at most $O(np)$ (and sometimes much less) avoiding an $O(np^2)$ least squares estimate. We describe the connection between $\Theta$-IPOD and $M$-estimators. Our proposed method has one tuning parameter with which to both identify outliers and estimate regression coefficients. A data-dependent choice can be made based on BIC. The tuned $\Theta$-IPOD shows outstanding performance in identifying outliers in various situations in comparison to other existing approaches. This methodology extends to high-dimensional modeling with $p\gg n$, if both the coefficient vector and the outlier pattern are sparse

The History of the iPad

The purpose of this paper is to review the history of the iPad and its influence over contemporary computing. Although the iPad is relatively new, the tablet computer is having a long and lasting affect on how we communicate. With this essay, I attempt to review the technologies that emerged and converged to create the tablet computer. Of course, Apple and its iPad are at the center of this new computing movement

Generation M2: Media in the Lives of 8- to 18-Year-Olds

Examines trends in which media youth use, for how much time, how new media platforms have affected media consumption, what role mobile and online media play, what media environment youth live in, and how patterns vary by gender, age, and race/ethnicity

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Power solutions in the field: Solar power for laptop computers

The task of language documentation is increasingly tied to computers, for processing both text and audio. Working in the field can create problems that many of us do not experience in our home countries. Many language communities live in remote locations where mains electricity is non-existent or unreliable. One solution to this problem involves using solar panels to capture electricity, and a car battery to store it. This paper summarises the authors' experiences with powering laptops using solar panels and car batteries during our recent fieldtrips to Nigeria