Parameter inference in ordinary differential equations is an important problem in many applied sciences and in engineering, especially in a data-scarce setting. In this work, we introduce a novel generative modeling approach based on constrained Gaussian processes and use it to create a computationally and data efficient algorithm for state and parameter inference. In an extensive set of experiments, our approach outperforms its competitors both in terms of accuracy and computational cost for parameter inference. It also shows promising results for the much more challenging problem of model selection.

Multiple sets of measurements on the same objects obtained from different platforms may reflect partially complementary information of the studied system. The integrative analysis of such data sets not only provides us with the opportunity of a deeper understanding of the studied system, but also introduces some new statistical challenges. First, the separation of information that is common across all or some of the data sets, and the information that is specific to each data set is problematic. Furthermore, these data sets are often a mix of quantitative and discrete (binary or categorical) data types, while commonly used data fusion methods require all data sets to be quantitative. In this paper, we propose an exponential family simultaneous component analysis (ESCA) model to tackle the potential mixed data types problem of multiple data sets. In addition, a structured sparse pattern of the loading matrix is induced through a nearly unbiased group concave penalty to disentangle the global, local common and distinct information of the multiple data sets. A Majorization-Minimization based algorithm is derived to fit the proposed model. Analytic solutions are derived for updating all the parameters of the model in each iteration, and the algorithm will decrease the objective function in each iteration monotonically. For model selection, a missing value based cross validation procedure is implemented. The advantages of the proposed method in comparison with other approaches are assessed using comprehensive simulations as well as the analysis of real data from a chronic lymphocytic leukaemia (CLL) study.

The method to derive uniform bounds with Gaussian and Rademacher complexities is extended to the case where the sample average is replaced by a nonlinear statistic. Tight bounds are obtained for U-statistics, smoothened L-statistics and error functionals of l2-regularized algorithms.

The stringent requirements for low-latency and privacy of the emerging high-stake applications with intelligent devices such as drones and smart vehicles make the cloud computing inapplicable in these scenarios. Instead, edge machine learning becomes increasingly attractive for performing training and inference directly at network edges without sending data to a centralized data center. This stimulates a nascent field termed as federated learning for training a machine learning model on computation, storage, energy and bandwidth limited mobile devices in a distributed manner. To preserve data privacy and address the issues of unbalanced and non-IID data points across different devices, the federated averaging algorithm has been proposed for global model aggregation by computing the weighted average of locally updated model at each selected device. However, the limited communication bandwidth becomes the main bottleneck for aggregating the locally computed updates. We thus propose a novel over-the-air computation based approach for fast global model aggregation via exploring the superposition property of a wireless multiple-access channel. This is achieved by joint device selection and beamforming design, which is modeled as a sparse and low-rank optimization problem to support efficient algorithms design. To achieve this goal, we provide a difference-of-convex-functions (DC) representation for the sparse and low-rank function to enhance sparsity and accurately detect the fixed-rank constraint in the procedure of device selection. A DC algorithm is further developed to solve the resulting DC program with global convergence guarantees. The algorithmic advantages and admirable performance of the proposed methodologies are demonstrated through extensive numerical results.

Recessions reflect great dislocation in the economy and are often the source of societal anxiety. During a recession, unemployment is usually higher, and output is lower. Accurately identifying turning points from expansions to recessions has broad use for policymakers, business executives, academics, and individuals. Additionally, investors with enough resources to use this information in their investment process may change their portfolios as the economy turns from growth to contraction. There have been several attempts in the literature to accurately predict the timing of recessions.

This post was featured in our Cognilytica Newsletter, with additional details. Everyone who has ever worked on a software project knows that you don't just simply put code and content out to your customers, employees, or stakeholders without first testing it to make sure it's not broken or dead on delivery. Quality Assurance (QA) is such a core part of any technology or business delivery that it's one of the essential components of any development methodology. And if you're doing this in an agile fashion, you do it in small, iterative chunks so you make sure to respond to the continuously evolving and changing needs of the customer. Surely AI projects are no different.

We consider a context-based dynamic pricing problem of online products which have low sales. Sales data from Alibaba, a major global online retailer, illustrate the prevalence of low-sale products. For these products, existing single-product dynamic pricing algorithms do not work well due to insufficient data samples. To address this challenge, we propose pricing policies that concurrently perform clustering over products and set individual pricing decisions on the fly. By clustering data and identifying products that have similar demand patterns, we utilize sales data from products within the same cluster to improve demand estimation and allow for better pricing decisions. We evaluate the algorithms using the regret, and the result shows that when product demand functions come from multiple clusters, our algorithms significantly outperform traditional single-product pricing policies. Numerical experiments using a real dataset from Alibaba demonstrate that the proposed policies, compared with several benchmark policies, increase the revenue. The results show that online clustering is an effective approach to tackling dynamic pricing problems associated with low-sale products. Our algorithms were further implemented in a field study at Alibaba with 40 products for 30 consecutive days, and compared to the products which use business-as-usual pricing policy of Alibaba. The results from the field experiment show that the overall revenue increased by 10.14%.

Distributed learning is central for large-scale training ofdeep-learning models. However, they are exposed to a security threat in which Byzantine participants can interrupt or control the learning process. Previous attack models and their corresponding defensesassume that the rogue participants are (a) omniscient (know the data of all other participants), and (b) introduce large change to the parameters. We show that small but wellcrafted changesare sufficient, leading to a novel non-omniscient attack on distributed learning that go undetected by all existing defenses. We demonstrate ourattack method works not only for preventing convergencebut also for repurposing of the model behavior ("backdooring"). We show that 20% of corrupt workers are sufficient to degrade aCIFAR10 model's accuracy by 50%, as well as to introduce backdoors into MNIST and CIFAR10 models without hurting their accuracy.

Imbalance data distribution is an important part of machine learning workflow. An imbalanced dataset means instances of one of the two classes is higher than the other, in another way, the number of observations is not the same for all the classes in a classification dataset. This problem is faced not only in the binary class data but also in the multi-class data. In this article, we list some important techniques that will help you to deal with your imbalanced data. This technique is used to modify the unequal data classes to create balanced datasets.

Other than the various cross-validation functions, the main functions are polyfit() and predict.polyFit(). One can fit either regression or classification models, with an option to perform PCA for dimension reduction on the predictors/features. Built in to the latest version of the regtools package. In the former case, getPE() reads in the dataset and does some preprocessing, producing a data frame pe. Forward stepwise regression is also available with FSR which also accepts polynomial degree and interaction as inputs.