Class Data Distribution Research Articles

Multi-reference source aircraft classification network based on unknown class prototype estimation

Abstract Gathering complete aircraft types for close-set tasks is challenging and costly in fine-grained aircraft classification, resulting in encountering unknown class aircraft images in real-world models. To address this problem, we propose a network called a multi-reference source fine-grained aircraft classification network (MRSN) to explicitly and implicitly distinguish known class boundaries and embed unknown classes into the sample space. Specifically, we propose an embedding module (UCPE) to synthesize an unknown class prototype to facilitate the modeling of unknown class data distribution. Besides, we introduce a concatenated multi-reference source module (CMS) that combines distance measurement and probability estimation to classify whether testing images are of unknown class or not. Our proposed MRSN innovatively extends the open-set learning paradigm to the fine-grained classification of geospatial objects rather than simple scene classification. Besides, it shows excellent performance in our constructed dataset, which demonstrates the effectiveness and progressiveness of our method.

An adaptive weighted ensemble learning network for diabetic retinopathy classification.

Diabetic retinopathy (DR) is one of the leading causes of blindness. However, because the data distribution of classes is not always balanced, it is challenging for automated early DR detection using deep learning techniques. In this paper, we propose an adaptive weighted ensemble learning method for DR detection based on optical coherence tomography (OCT) images. Specifically, we develop an ensemble learning model based on three advanced deep learning models for higher performance. To better utilize the cues implied in these base models, a novel decision fusion scheme is proposed based on the Bayesian theory in terms of the key evaluation indicators, to dynamically adjust the weighting distribution of base models to alleviate the negative effects potentially caused by the problem of unbalanced data size. Extensive experiments are performed on two public datasets to verify the effectiveness of the proposed method. A quadratic weighted kappa of 0.8487 and an accuracy of 0.9343 on the DRAC2022 dataset, and a quadratic weighted kappa of 0.9007 and an accuracy of 0.8956 on the APTOS2019 dataset are obtained, respectively. The results demonstrate that our method has the ability to enhance the ovearall performance of DR detection on OCT images.

Resampling ensemble model based on data distribution for imbalanced credit risk evaluation in P2P lending

The misclassification of loan applicants by credit scoring model is one of the main factors causing the loss of investors’ profits in P2P lending. Class imbalance of credit data is a main factor that affects classification performance of the model. Most existing methods of addressing class imbalance in credit scoring worked on improving the prediction accuracy for minority class samples (bad credit), which usually led to decreasing the prediction performance for majority class samples (good credit) significantly. In this paper, we propose a novel resampling ensemble model based on data distribution (REMDD) for imbalanced credit risk evaluation in P2P lending. REMMD solves class imbalance problem by using proposed undersampling method based on majority class data distribution (UMCDD). To further improve classification performance of REMMD, base classifiers with better comprehensive performance on the validation set are used to conduct class prediction. We validate the classification performance of REMDD on the three real and representative P2P lending credit datasets. The experimental results demonstrate that REMDD not only has good prediction performance for both majority class and minority class, but also effectively improves the comprehensive classification performance for imbalanced credit risk evaluation in P2P lending, compared with existing models.

Zero and Few Shot Learning With Semantic Feature Synthesis and Competitive Learning.

Zero-shot learning (ZSL) is made possible by learning a projection function between a feature space and a semantic space (e.g., an attribute space). Key to ZSL is thus to learn a projection that is robust against the often large domain gap between the seen and unseen class domains. In this work, this is achieved by unseen class data synthesis and robust projection function learning. Specifically, a novel semantic data synthesis strategy is proposed, by which semantic class prototypes (e.g., attribute vectors) are used to simply perturb seen class data for generating unseen class ones. As in any data synthesis/hallucination approach, there are ambiguities and uncertainties on how well the synthesised data can capture the targeted unseen class data distribution. To cope with this, the second contribution of this work is a novel projection learning model termed competitive bidirectional projection learning (BPL) designed to best utilise the ambiguous synthesised data. Specifically, we assume that each synthesised data point can belong to any unseen class; and the most likely two class candidates are exploited to learn a robust projection function in a competitive fashion. As a third contribution, we show that the proposed ZSL model can be easily extended to few-shot learning (FSL) by again exploiting semantic (class prototype guided) feature synthesis and competitive BPL. Extensive experiments show that our model achieves the state-of-the-art results on both problems.

Minority Oversampling in Kernel Adaptive Subspaces for Class Imbalanced Datasets

The class imbalance problem in machine learning occurs when certain classes are underrepresented relative to the others, leading to a learning bias toward the majority classes. To cope with the skewed class distribution, many learning methods featuring minority oversampling have been proposed, which are proved to be effective. To reduce information loss during feature space projection, this study proposes a novel oversampling algorithm, named minority oversampling in kernel adaptive subspaces (MOKAS), which exploits the invariant feature extraction capability of a kernel version of the adaptive subspace self-organizing maps. The synthetic instances are generated from well-trained subspaces and then their pre-images are reconstructed in the input space. Additionally, these instances characterize nonlinear structures present in the minority class data distribution and help the learning algorithms to counterbalance the skewed class distribution in a desirable manner. Experimental results on both real and synthetic data show that the proposed MOKAS is capable of modeling complex data distribution and outperforms a set of state-of-the-art oversampling algorithms.

A Normalized Probabilistic Expectation-Maximization Neural Network for Minimizing Bayesian Misclassification Cost Risk

In this paper, we propose a normalized semi-supervised probabilistic expectation-maximization neural network (PEMNN) that minimizes Bayesian misclassification cost risk. Using simulated and real-world datasets, we compare the proposed PEMNN with supervised cost sensitive probabilistic neural network (PNN), discriminant analysis (DA), mathematical integer programming (MIP) model and support vector machines (SVM) for different misclassification cost asymmetries and class biases. The results of our experiments indicate that the PEMNN performs better when class data distributions are normal or uniform. However, when class data distribution is exponential the performance of PEMNN deteriorates giving slight advantage to competing MIP, DA, PNN and SVM techniques. For real-world data with non-parametric distributions and mixed decision-making attributes (continuous and categorical), the PEMNN outperforms the PNN.

Multiclass Kernel Function Evaluation

Kernel is a key component of the support vector machines (SVMs) and other kernel methods. Based on the data distributions of classes in the feature space, this paper proposed a model selection criterion to evaluate the goodness of a kernel in multiclass classification scenario. This criterion is computationally efficient and is differentiable with respect to the kernel parameters. Compared with the k-fold cross validation technique which is often regarded as a benchmark, this criterion is found to yield about the same performance with much less computational overhead.

DEA based data preprocessing for maximum decisional efficiency linear case valuation models

In this paper, we use data envelopment analysis (DEA) to preprocess training data cases before the maximum decisional efficiency (MDE) principle is used to estimate discriminant function parameters. Using an example from the literature and simulated datasets, we compare the performance of DEA-MDE procedure for parameter estimation with traditional MDE procedure without data preprocessing. The results of our experiments indicate that the DEA-MDE procedure eliminates some inconsistencies caused by MDE principle, provides results that are consistent with an ensemble of expert decisions, reduces dimensionality of examples used in training datasets, and performs equal to or better than the MDE procedure for holdout sample tests. The DEA-MDE procedure appears to be sensitive to class data distribution and best results are obtained when a class data distribution is exponential.

An efficient kernel matrix evaluation measure

We study the problem of evaluating the goodness of a kernel matrix for a classification task. As kernel matrix evaluation is usually used in other expensive procedures like feature and model selections, the goodness measure must be calculated efficiently. Most previous approaches are not efficient except for kernel target alignment (KTA) that can be calculated in O ( n 2 ) time complexity. Although KTA is widely used, we show that it has some serious drawbacks. We propose an efficient surrogate measure to evaluate the goodness of a kernel matrix based on the data distributions of classes in the feature space. The measure not only overcomes the limitations of KTA but also possesses other properties like invariance, efficiency and an error bound guarantee. Comparative experiments show that the measure is a good indication of the goodness of a kernel matrix.