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Vanessa Gómez-Verdejo - IEEE Xplore Author Profile

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Adaptive learning is necessary for nonstationary environments where the learning machine needs to forget past data distribution. Efficient algorithms require a compact model update to not grow in computational burden with the incoming data and with the lowest possible computational cost for online parameter updating. Existing solutions only partially cover these needs. Here, we propose the first a...Show More
Audio or visual data analysis tasks usually have to deal with high-dimensional and nonnegative signals. However, most data analysis methods suffer from overfitting and numerical problems when data have more than a few dimensions needing a dimensionality reduction preprocessing. Moreover, interpretability about how and why filters work for audio or visual applications is a desired property, especia...Show More
During the past years solar radiation prediction has become increasingly relevant among the scientific community and Machine Learning techniques have proven to be a useful tool to automatically learn an accurate prediction model. In this paper, we move one step further and try to gain interpretability during the learning process by introducing a novel feature selection approach. Our method trains ...Show More
Multivariate Analysis (MVA) comprises a collection of tools that play a fundamental role in statistical data analysis. These techniques have become increasingly popular since the proposal of Principal Component Analysis (PCA) in 1901 [1]. PCA was proposed as a simple and efficient way to reduce data dimension by projecting the data over the largest variance directions. As illustrated in Fig. 1, PC...Show More
This paper investigates a new measure of voxel importance based on analysing the sign consistency of voxels in an ensemble of linear SVM classifiers. The ensemble is endowed with a significant degree of diversity since the training set for each individual classifier is a random subsample of the initial training set. The importance of a voxel is proportional to the number of times that the voxel's ...Show More
Orthonormalized partial least squares (OPLS) is a popular multivariate analysis method to perform supervised feature extraction. In this paper, we propose a novel scheme to solve Orthonormalized Partial Least Squares (OPLS) that can be easily modified to include additional constraints over the input data projection vectors. This scheme is used to implement an OPLSmethod with sparsity constraints (...Show More
In this brief, we propose to increase the capabilities of standard real AdaBoost (RAB) architectures by replacing their linear combinations with a fusion controlled by a gate with fixed kernels. Experimental results in a series of well-known benchmark problems support the effectiveness of this approach in improving classification performance. Although the need for cross-validation processes obviou...Show More
In this work we apply a multivariate feature selection method based on bagging linear SVMs to construct a classifier able to differentiate among control subjects and patients with obsessive compulsive disorder (OCD). Our method selects sets of voxels that are relevant for the detection of the disease. The voxel selection is completed with a conformal analysis based refinement that controls over fi...Show More
Functional Magnetic Resonance Imaging is a technique for the study of the human brain that can detect the regionally specific effects of brain stimuli or activity through the detection of the activity related BOLD signal. The standard fMRI techniques include the use of the so called General Linear Model (GLM), which assumes that the combination of different activity in the brain present linear beh...Show More
This paper introduces a new support vector machine (SVM) formulation to obtain sparse solutions in the primal SVM parameters, providing a new method for feature selection based on SVMs. This new approach includes additional constraints to the classical ones that drop the weights associated to those features that are likely to be irrelevant. A ν-SVM formulation has been used, where ν indicates the ...Show More
In this correspondence, we derive an online adaptive one-class support vector machine. The machine structure is updated via growing and pruning mechanisms and the weights are updated using structural risk minimization principles underlying support vector machines. Our approach leads to very compact machines compared to other online kernel methods whose size, unless truncated, grows almost linearly...Show More
This work explores the possibility of improving the performance of Real Adaboost ensemble classifiers by replacing their standard linear combination of learners by a gating scheme. This more powerful fusion method is defined following the epoch-by-epoch construction of boosting ensembles. Preliminary experimental results support the potential of this new approach.Show More
Progressively emphasizing samples that are difficult to classify correctly is the base for the recognized high performance of real Adaboost (RA) ensembles. The corresponding emphasis function can be written as a product of a factor that measures the quadratic error and a factor related to the proximity to the classification border; this fact opens the door to explore the potential advantages provi...Show More
The recent interest in combining neural networks has produced a variety of techniques. This paper deals with boosting methods, in particular, real AdaBoost schemes built up with radial basis function networks. Real Adaboost emphasis function can be divided into two different terms, the first only focus on the quadratic error of each pattern and the second only takes into account its "proximity" to...Show More
Among all adaptive filtering algorithms, Widrow and Hoff's least mean square (LMS) has probably become the most popular because of its robustness, good tracking properties and simplicity. A drawback of LMS is that the step size implies a compromise between speed of convergence and final misadjustment. To combine different speed LMS filters serves to alleviate this compromise, as it was demonstrate...Show More
The Least Mean Square (LMS) algorithm has become a very popular algorithm for adaptive filtering due to its robustness and simplicity. An adaptive convex combination of one fast a one slow LMS filters has been previously proposed for plant identification, as a way to break the speed vs precision compromise inherent to LMS filters. In this paper, an improved version of this combination method is pr...Show More
The least mean square (LMS) algorithm has become a very popular algorithm for adaptive filtering due to its robustness and simplicity. A difficulty concerning LMS filters is their inherent compromise between tracking capabilities and precision, that is imposed by the selection of a fixed value for the adaption step. An adaptive convex combination of one fast LMS filter (high adaption step) and one...Show More