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We propose database-aware regression methods for extrapolation from few measurements in the context of quantitative prognosis. The idea is to leverage a database of patients with similar conditions to increase the effective number of samples when we train a predictive model. Applying the proposed method to a database of glaucoma patients, we were able to predict the disease condition at a future time point significantly more accurately than the conventional patient-wise linear regression approach. In fact, our prediction was 50% more accurate than the conventional approach when three or less measurements were available and with only two measurements at least as accurate as the conventional approach with six measurements. Moreover, the proposed method can provide spatially localized prediction and also the (localized) speed of progression, which are valuable for doctors in making decisions.

Non-negative Tensor Factorization (NTF) is a widely used technique for decomposing a non-negative value tensor into sparse and reasonably interpretable factors. However, NTF performs poorly when the tensor is extremely sparse, which is often the case with real-world data and higher-order tensors. In this paper, we propose Non-negative Multiple Tensor Factorization (NMTF), which factorizes the target tensor and auxiliary tensors simultaneously. Auxiliary data tensors compensate for the sparseness of the target data tensor. The factors of the auxiliary tensors also allow us to examine the target data from several different aspects. We experimentally confirm that NMTF performs better than NTF in terms of reconstructing the given data. Furthermore, we demonstrate that the proposed NMTF can successfully extract spatio-temporal patterns of people's daily life such as leisure, drinking, and shopping activity by analyzing several tensors extracted from online review data sets.

Personalized activity recognition usually faces the problem of data sparseness. We aim at improving accuracy of personalized activity recognition by incorporating the information from other persons. We propose a new online multi-task learning method for personalized activity recognition. The proposed online multi-task learning method automatically learns the ``transfer-factors" (similarities) among different tasks (i.e., among different persons in our case). Experiments demonstrate that the proposed method significantly outperforms existing methods. The novelty of this paper is twofold: (1) A new multi-task learning framework, which can naturally learn similarities among tasks, (2) To our knowledge, this is the first study of large-scale personalized activity recognition.

Detection of emerging topics are now receiving renewed interest motivated by the rapid growth of social networks. Conventional term-frequency-based approaches may not be appropriate in this context, because the information exchanged are not only texts but also images, URLs, and videos. We focus on the social aspects of theses networks. That is, the links between users that are generated dynamically intentionally or unintentionally through replies, mentions, and retweets. We propose a probability model of the mentioning behaviour of a social network user, and propose to detect the emergence of a new topic from the anomaly measured through the model. We combine the proposed mention anomaly score with a recently proposed change-point detection technique based on the Sequentially Discounting Normalized Maximum Likelihood (SDNML), or with Kleinberg's burst model. Aggregating anomaly scores from hundreds of users, we show that we can detect emerging topics only based on the reply/mention relationships in social network posts. We demonstrate our technique in a number of real data sets we gathered from Twitter. The experiments show that the proposed mention-anomaly-based approaches can detect new topics at least as early as the conventional term-frequency-based approach, and sometimes much earlier when the keyword is ill-defined., Comment: 10 pages, 6 figures