Statistical Learning
Patch-level Neighborhood Interpolation: A General and Effective Graph-based Regularization Strategy
Sun, Ke, Yu, Bing, Lin, Zhouchen, Zhu, Zhanxing
Regularization plays a crucial role in machine learning models, especially for deep neural networks. The existing regularization techniques mainly reply on the i.i.d. assumption and only employ the information of the current sample, without the leverage of neighboring information between samples. In this work, we propose a general regularizer called Patch-level Neighborhood Interpolation~(\textbf{Pani}) that fully exploits the relationship between samples. Furthermore, by explicitly constructing a patch-level graph in the different network layers and interpolating the neighborhood features to refine the representation of the current sample, our Patch-level Neighborhood Interpolation can then be applied to enhance two popular regularization strategies, namely Virtual Adversarial Training (VAT) and MixUp, yielding their neighborhood versions. The first derived \textbf{Pani VAT} presents a novel way to construct non-local adversarial smoothness by incorporating patch-level interpolated perturbations. In addition, the \textbf{Pani MixUp} method extends the original MixUp regularization to the patch level and then can be developed to MixMatch, achieving the state-of-the-art performance. Finally, extensive experiments are conducted to verify the effectiveness of the Patch-level Neighborhood Interpolation in both supervised and semi-supervised settings.
Large-scale Multi-view Subspace Clustering in Linear Time
Kang, Zhao, Zhou, Wangtao, Zhao, Zhitong, Shao, Junming, Han, Meng, Xu, Zenglin
A plethora of multi-view subspace clustering (MVSC) methods have been proposed over the past few years. Researchers manage to boost clustering accuracy from different points of view. However, many state-of-the-art MVSC algorithms, typically have a quadratic or even cubic complexity, are inefficient and inherently difficult to apply at large scales. In the era of big data, the computational issue becomes critical. To fill this gap, we propose a large-scale MVSC (LMVSC) algorithm with linear order complexity. Inspired by the idea of anchor graph, we first learn a smaller graph for each view. Then, a novel approach is designed to integrate those graphs so that we can implement spectral clustering on a smaller graph. Interestingly, it turns out that our model also applies to single-view scenario.
Imputing missing values with unsupervised random trees
When designing statistical models from tabular data for supervised learning tasks such as regression or classification, oftentimes it happens that some of th e observations available for fitting such models are missing values in one or more variables, usually d ue to reasons such as poor data collection practices, loss of information, participants dropping out of a survey, or similar. Many methods such as [2] or [4] overcome this issue by using heuristics to handle missing information - decision tree methods in particular, due to their splitting nature that takes one variable at a time, are particularly well suited for implicit han dling of missing data without a-priori imputation ([16]), but other methods such as gene ralized linear models or support vector machines cannot handle missing values in the same wa y, and when using them on a dataset with missing entries, these entries have to either be dr opped or imputed. Typical strategies for imputing the missing entries include: replacing them with the column mean or median, determining the most similar observations (nearest neighbors) according to the non-missing variables and taking a simple or weighted average of the m issing variable(s) from them ([11]), producing a latent representation of the data by some low-rank matrix factorization that minimizes errors on the non-missing entries and from which the m issing entries are then reconstructed ([10]), and iterative imputation that starts with so me basic imputation for all values and then cycles through each variable by constructing a mod el to predict the missing values from the non-missing observations, replacing the earlier impu tation with the model prediction and repeating until convergence ([3], [18]).
LMLFM: Longitudinal Multi-Level Factorization Machine
Liang, Junjie, Xu, Dongkuan, Sun, Yiwei, Honavar, Vasant
We consider the problem of learning predictive models from longitudinal data, consisting of irregularly repeated, sparse observations from a set of individuals over time. Such data often exhibit {\em longitudinal correlation} (LC) (correlations among observations for each individual over time), {\em cluster correlation} (CC) (correlations among individuals that have similar characteristics), or both. These correlations are often accounted for using {\em mixed effects models} that include {\em fixed effects} and {\em random effects}, where the fixed effects capture the regression parameters that are shared by all individuals, whereas random effects capture those parameters that vary across individuals. However, the current state-of-the-art methods are unable to select the most predictive fixed effects and random effects from a large number of variables, while accounting for complex correlation structure in the data and non-linear interactions among the variables. We propose Longitudinal Multi-Level Factorization Machine (LMLFM), to the best of our knowledge, the first model to address these challenges in learning predictive models from longitudinal data. We establish the convergence properties, and analyze the computational complexity, of LMLFM. We present results of experiments with both simulated and real-world longitudinal data which show that LMLFM outperforms the state-of-the-art methods in terms of predictive accuracy, variable selection ability, and scalability to data with large number of variables. The code and supplemental material is available at \url{https://github.com/junjieliang672/LMLFM}.
Schemaless Queries over Document Tables with Dependencies
Canim, Mustafa, Cornelio, Cristina, Iyengar, Arun, Musa, Ryan, Muro, Mariano Rodrigez
Unstructured enterprise data such as reports, manuals and guidelines often contain tables. The traditional way of integrating data from these tables is through a two-step process of table detection/extraction and mapping the table layouts to an appropriate schema. This can be an expensive process. In this paper we show that by using semantic technologies (RDF/SPARQL and database dependencies) paired with a simple but powerful way to transform tables with non-relational layouts, it is possible to offer query answering services over these tables with minimal manual work or domain-specific mappings. Our method enables users to exploit data in tables embedded in documents with little effort, not only for simple retrieval queries, but also for structured queries that require joining multiple interrelated tables.
Rule Extraction in Unsupervised Anomaly Detection for Model Explainability: Application to OneClass SVM
Barbado, Alberto, Corcho, รscar
OneClass SVM is a popular method for unsupervised anomaly detection. As many other methods, it suffers from the \textit{black box} problem: it is difficult to justify, in an intuitive and simple manner, why the decision frontier is identifying data points as anomalous or non anomalous. Such type of problem is being widely addressed for supervised models. However, it is still an uncharted area for unsupervised learning. In this paper, we describe a method to infer rules that justify why a point is labelled as an anomaly, so as to obtain intuitive explanations for models created using the OneClass SVM algorithm. We evaluate our proposal with different datasets, including real-world data coming from industry. With this, our proposal contributes to extend Explainable AI techniques to unsupervised machine learning models.
How to Become a Data Scientist
If you do know what a Data Scientist is, you are rare to find, as since even the most experienced professionals still have difficulty defining the scope of the area. One possible delimitation is that the data scientist is the person responsible for producing predictive and / or explanatory models using machine learning and statistics.
Machine Learning with Python Business Applications AI Robot
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Gradient-based Optimization for Bayesian Preference Elicitation
Vendrov, Ivan, Lu, Tyler, Huang, Qingqing, Boutilier, Craig
Effective techniques for eliciting user preferences have taken on added importance as recommender systems (RSs) become increasingly interactive and conversational. A common and conceptually appealing Bayesian criterion for selecting queries is expected value of information (EVOI) . Unfortunately, it is computationally prohibitive to construct queries with maximum EVOI in RSs with large item spaces. We tackle this issue by introducing a continuous formulation of EVOI as a differentiable network that can be optimized using gradient methods available in modern machine learning (ML) computational frameworks (e.g., TensorFlow, PyTorch). We exploit this to develop a novel, scalable Monte Carlo method for EVOI optimization, which is more scalable for large item spaces than methods requiring explicit enumeration of items. While we emphasize the use of this approach for pairwise (or k -wise) comparisons of items, we also demonstrate how our method can be adapted to queries involving subsets of item attributes or "partial items," which are often more cognitively manageable for users. Experiments show that our gradient-based EVOI technique achieves state-of-the-art performance across several domains while scaling to large item spaces.
A semiparametric instrumental variable approach to optimal treatment regimes under endogeneity
Cui, Yifan, Tchetgen, Eric Tchetgen
There is a fast-growing literature on estimating optimal treatment regimes based on randomized trials or observational studies under a key identifying condition of no unmeasured confounding. Because confounding by unmeasured factors cannot generally be ruled out with certainty in observational studies or randomized trials subject to noncompliance, we propose a general instrumental variable approach to learning optimal treatment regimes under endogeneity. Specifically, we provide sufficient conditions for the identification of both value function $E[Y_{\cD(L)}]$ for a given regime $\cD$ and optimal regime $\arg \max_{\cD} E[Y_{\cD(L)}]$ with the aid of a binary instrumental variable, when no unmeasured confounding fails to hold. We establish consistency of the proposed weighted estimators. We also extend the proposed method to identify and estimate the optimal treatment regime among those who would comply to the assigned treatment under monotonicity. In this latter case, we establish the somewhat surprising result that the complier optimal regime can be consistently estimated without directly collecting compliance information and therefore without the complier average treatment effect itself being identified. Furthermore, we propose novel semiparametric locally efficient and multiply robust estimators. Our approach is illustrated via extensive simulation studies and a data application on the effect of child rearing on labor participation.