Browsing by Author "Delibalta, İ."

Now showing 1 - 11 of 11

Open Access
Adaptive hierarchical space partitioning for online classification
(IEEE, 2016) Kılıç, O. Fatih; Vanlı, N. D.; Özkan, H.; Delibalta, İ.; Kozat, Süleyman Serdar
We propose an online algorithm for supervised learning with strong performance guarantees under the empirical zero-one loss. The proposed method adaptively partitions the feature space in a hierarchical manner and generates a powerful finite combination of basic models. This provides algorithm to obtain a strong classification method which enables it to create a linear piecewise classifier model that can work well under highly non-linear complex data. The introduced algorithm also have scalable computational complexity that scales linearly with dimension of the feature space, depth of the partitioning and number of processed data. Through experiments we show that the introduced algorithm outperforms the state-of-the-art ensemble techniques over various well-known machine learning data sets.
Open Access
Big data signal processing using boosted RLS algorithm
(IEEE, 2016) Civek, Burak Cevat; Kari, Dariush; Delibalta, İ.; Kozat, Süleyman Serdar
We propose an efficient method for the high dimensional data regression. To this end, we use a least mean squares (LMS) filter followed by a recursive least squares (RLS) filter and combine them via boosting notion extensively used in machine learning literature. Moreover, we provide a novel approach where the RLS filter is updated randomly in order to reduce the computational complexity while not giving up more on the performance. In the proposed algorithm, after the LMS filter produces an estimate, depending on the error made on this step, the algorithm decides whether or not updating the RLS filter. Since we avoid updating the RLS filter for all data sequence, the computational complexity is significantly reduced. Error performance and the computation time of our algorithm is demonstrated for a highly realistic scenario.
Open Access
Boosted LMS-based piecewise linear adaptive filters
(IEEE, 2016) Kari, Dariush; Marivani, Iman; Delibalta, İ.; Kozat, Süleyman Serdar
We introduce the boosting notion extensively used in different machine learning applications to adaptive signal processing literature and implement several different adaptive filtering algorithms. In this framework, we have several adaptive constituent filters that run in parallel. For each newly received input vector and observation pair, each filter adapts itself based on the performance of the other adaptive filters in the mixture on this current data pair. These relative updates provide the boosting effect such that the filters in the mixture learn a different attribute of the data providing diversity. The outputs of these constituent filters are then combined using adaptive mixture approaches. We provide the computational complexity bounds for the boosted adaptive filters. The introduced methods demonstrate improvement in the performances of conventional adaptive filtering algorithms due to the boosting effect.
Open Access
Mathematical model of causal inference in social networks
(IEEE, 2016) Şimsek, Mustafa; Delibalta, İ.; Baruh, L.; Kozat, Süleyman Serdar
In this article, we model the effects of machine learning algorithms on different Social Network users by using a causal inference framework, making estimation about the underlying system and design systems to control underlying latent unobservable system. In this case, the latent internal state of the system can be a wide range of interest of user. For example, it can be a user's preferences for some certain products or affiliation of the user to some political parties. We represent these variables using state space model. In this model, the internal state of the system, e.g. the preferences or affiliations of the user is observed using user's connections with the Social Networks such as Facebook status updates, shares, comments, blogs, tweets etc.
Open Access
Mixture of set membership filters approach for big data signal processing
(IEEE, 2016) Kılıç, O. Fatih; Sayın, M. Ömer; Delibalta, İ.; Kozat, Süleyman Serdar
In this work, we propose a new approach for mixture of adaptive filters based on set-membership filters (SMF) which is specifically designated for big data signal processing applications. By using this approach, we achieve significantly reduced computational load for the mixture methods with better performance in convergence rate and steady-state error with respect to conventional mixture methods. Finally, we approve these statements with the simulations done on produce data.
Open Access
Nonlinear regression using second order methods
(IEEE, 2016) Civek, Burak Cevat; Delibalta, İ.; Kozat, Süleyman Serdar
We present a highly efficient algorithm for the online nonlinear regression problem. We process only the currently available data and do not reuse it, hence, there is no need for storage. For the nonlinear regression, we use piecewise linear modeling, where the regression space is partitioned into several regions and a linear model is fit to each region. As the first time in the literature, we use second order methods, e.g. Newton-Raphson Methods, and adaptively train both the region boundaries and the corresponding linear models. Therefore, we overcome the well known overfitting and underfitting problems. The proposed algorithm provides a substantial improvement in the performance compared to the state of the art.
Open Access
Online adaptive hierarchical space partitioning classifier
(IEEE, 2016) Kılıç, O. Fatih; Vanlı, N. D.; Özkan, Hüseyin; Delibalta, İ.; Kozat, Süleyman Serdar
We introduce an on-line classification algorithm based on the hierarchical partitioning of the feature space which provides a powerful performance under the defined empirical loss. The algorithm adaptively partitions the feature space and at each region trains a different classifier. As a final classification result algorithm adaptively combines the outputs of these basic models which enables it to create a linear piecewise classifier model that can work well under highly non-linear complex data. The introduced algorithm also have scalable computational complexity that scales linearly with dimension of the feature space, depth of the partitioning and number of processed data. Through experiments we show that the introduced algorithm outperforms the state-of-the-art ensemble techniques over various well-known machine learning data sets.
Open Access
Online churn detection on high dimensional cellular data using adaptive hierarchical trees
(IEEE, 2016) Khan, Farhan; Delibalta, İ.; Kozat, Süleyman Serdar
We study online sequential logistic regression for churn detection in cellular networks when the feature vectors lie in a high dimensional space on a time varying manifold. We escape the curse of dimensionality by tracking the subspace of the underlying manifold using a hierarchical tree structure. We use the projections of the original high dimensional feature space onto the underlying manifold as the modified feature vectors. By using the proposed algorithm, we provide significant classification performance with significantly reduced computational complexity as well as memory requirement. We reduce the computational complexity to the order of the depth of the tree and the memory requirement to only linear in the intrinsic dimension of the manifold. We provide several results with real life cellular network data for churn detection.
Open Access
Online text classification for real life tweet analysis
(IEEE, 2016) Yar, Ersin; Delibalta, İ.; Baruh, L.; Kozat, Süleyman Serdar
In this paper, we study multi-class classification of tweets, where we introduce highly efficient dimensionality reduction techniques suitable for online processing of high dimensional feature vectors generated from freely-worded text. As for the real life case study, we work on tweets in the Turkish language, however, our methods are generic and can be used for other languages as clearly explained in the paper. Since we work on a real life application and the tweets are freely worded, we introduce text correction, normalization and root finding algorithms. Although text processing and classification are highly important due to many applications such as emotion recognition, advertisement selection, etc., online classification and regression algorithms over text are limited due to need for high dimensional vectors to represent natural text inputs. We overcome such limitations by showing that randomized projections and piecewise linear models can be efficiently leveraged to significantly reduce the computational cost for feature vector extraction from the tweets. Hence, we can perform multi-class tweet classification and regression in real time. We demonstrate our results over tweets collected from a real life case study where the tweets are freely-worded, e.g., with emoticons, shortened words, special characters, etc., and are unstructured. We implement several well-known machine learning algorithms as well as novel regression methods and demonstrate that we can significantly reduce the computational complexity with insignificant change in the classification and regression performance.
Open Access
Piecewise linear regression based on adaptive tree structure using second order methods
(IEEE, 2016) Civek, Burak Cevat; Delibalta, İ.; Kozat, Süleyman Serdar
We introduce a highly efficient online nonlinear regression algorithm. We process the data in a truly online manner such that no storage is needed, i.e., the data is discarded after used. For nonlinear modeling we use a hierarchical piecewise linear approach based on the notion of decision trees, where the regressor space is adaptively partitioned based directly on the performance. As the first time in the literature, we learn both the piecewise linear partitioning of the regressor space as well as the linear models in each region using highly effective second order methods, i.e., Newton-Raphson Methods. Hence, we avoid the well known over fitting issues and achieve substantial performance compared to the state of the art. We demonstrate our gains over the well known benchmark data sets and provide performance results in an individual sequence manner guaranteed to hold without any statistical assumptions.
Open Access
A tree-based solution to nonlinear regression problem
(IEEE, 2016) Demir, Oğuzhan; Neyshabouri, Mohammadreza Mohaghegh; Delibalta, İ.; Kozat, Süleyman Serdar
In this paper, we offer and examine a new algorithm for sequential nonlinear regression problem. In this architecture, we use piecewise adaptive linear functions to find the nonlinear regression model sequentially. For more accurate and faster convergence, we combine a large class of piecewise linear functions. These piecewise linear functions are constructed by composing different adaptive linear functions, which are represented by the nodes of a lexicographical tree. With this tree structure, computational complexity of the algorithm is significantly reduced. To show the performance of the proposed algorithm, we present a simulation which is performed by using a well-known real data set.