Number Of Discriminative Features Research Articles

Code Review Knowledge Perception: Fusing Multi-Features for Salient-Class Location

Code review is a common software engineering practice of practical importance to reduce software defects. Review today is often with the help of specialized tools, such as Gerrit. However, even in a tool-supported code review involves a significant amount of human effort to understand the code change, because the information required to inspect code changes may distribute across multiple files that reviewers are not familiar with. Code changes are often organized as commits for review. In this paper, we found that most of the commits contain a salient class(es), which is saliently modified and causes the modification of the rest classes in a commit. Our user studies confirmed that identifying the salient class in a commit can facilitate reviewers in understanding code change. Inspired by the effectiveness of machine learning techniques in the classification field, we model the salient class identification as a binary classification problem and a number of discriminative features is extracted for a commit and used to characterize the salience of a class. The experiments results show that our approach achieves an accuracy of 88 percent. A user study with industrial developers shows that our approach can really improve the efficiency of reviewers understanding code changes in a reviewing scenario without using comment.

Visual Stimuli for P300-Based Brain-Computer Interfaces: Color, Shape, and Mobility

The purpose of this study was to identify the impact of different discriminative features of stimuli in a P300 brain-computer interface paradigm on overall performance and evoked potentials. It has been shown that stimuli sets with a greater number of discriminative features yield better target selection accuracy. Target selection accuracy was significantly higher for the stimuli that differ from each other by color, shape, and semantics. Highest performance was achieved with the stimuli set containing the largest number of discriminative features, namely a set of nine different-colored letters. This result is mainly due to higher mean P300 peak amplitude for stimuli sets that contain more discriminative features. The results of the study can be used for designing a better user experience in brain-computer interfacing (BCI). Motion of the stimuli presentation point and characteristics of this motion (linear or pseudorandom) did not have any impact on BCI performance. This result is promising for future BCI designs with rapid serial visual presentation using mobile robots or augmented reality as stimuli presentation environment.

Lymph Diseases Prediction Using Random Forest and Particle Swarm Optimization

This research aims to develop a model to enhance lymphatic diseases diagnosis by the use of random forest ensemble machine-learning method trained with a simple sampling scheme. This study has been carried out in two major phases: feature selection and classification. In the first stage, a number of discriminative features out of 18 were selected using PSO and several feature selection techniques to reduce the features dimension. In the second stage, we applied the random forest ensemble classification scheme to diagnose lymphatic diseases. While making experiments with the selected features, we used original and resampled distributions of the dataset to train random forest classifier. Experimental results demonstrate that the proposed method achieves a remark-able improvement in classification accuracy rate.

Feature selection with spatial path coding for multimedia analysis

The selection of a subset of discriminative features for semantic recognition is crucial to making multimedia analysis more interpretable. This paper proposes a model of spatial path coding (SPC) that uses a supervised technique to select sparse features. SPC is a regularized penalty that encodes the spatial correlations of features obtained by the spatial pyramid model. In SPC, each feature dimension is considered as a vertex in a direct acyclic graph (DAG), and the spatial correlations among features are considered as directed edges associated with predefined weights. Thus, the process of supervised feature selection can be directly formulated to solve a path selection problem with minimum cost. Experiments are conducted to evaluate the performance of supervised feature selection with SPC for the tasks of scene classification and action recognition using four benchmark datasets. The results show that SPC can be used to automatically select a subgraph of the DAG with a small number of discriminative features for a certain category. In addition, the method proposed in this paper shows better performance in terms of classification and recognition accuracy as compared with state-of-the-art algorithms.

Detection of frame deletion for digital video forensics

The abundance of digital video forms a potential piece of evidence in courtrooms. Augmenting subjective assessment of digital video evidence by an automated objective assessment helps increase the accuracy of deciding whether or not to admit the digital video as legal evidence. This paper examines the authenticity of digital video evidence and in particular it proposes a machine learning approach to detecting frame deletion. A number of discriminative features are extracted from the video bit stream and its reconstructed images. The features are based on prediction residuals, percentage of intra-coded macroblocks, quantization scales and reconstruction quality. The importance of these features is verified by using stepwise regression. Consequently, the dimensionality of the feature vectors is reduced using spectral regression where it is shown that the projected features of unaltered and forged videos are nearly separable. Machine learning techniques are used to report the true positive and false negative rates of the proposed solution. It is shown that the proposed solution works for detecting forged videos regardless of the number of deleted frames, as long as it is not a multiple of the length of a group of pictures. It is also shown that the proposed solution is applicable for the two modes of video compression, variable and constant bitrate coding.

Who is LB1? Discriminant analysis for the classification of specimens

Many problems in paleontology reduce to finding those features that best discriminate among a set of classes. A clear example is the classification of new specimens. However, these classifications are generally challenging because the number of discriminant features and the number of samples are limited. This has been the fate of LB1, a new specimen found in the Liang Bua Cave of Flores. Several authors have attributed LB1 to a new species of Homo, H. floresiensis. According to this hypothesis, LB1 is either a member of the early Homo group or a descendent of an ancestor of the Asian H. erectus. Detractors have put forward an alternate hypothesis, which stipulates that LB1 is in fact a microcephalic modern human. In this paper, we show how we can employ a new Bayes optimal discriminant feature extraction technique to help resolve this type of issues. In this process, we present three types of experiments. First, we use this Bayes optimal discriminant technique to develop a model of morphological (shape) evolution from Australopiths to H. sapiens. LB1 fits perfectly in this model as a member of the early Homo group. Second, we build a classifier based on the available cranial and mandibular data appropriately normalized for size and volume. Again, LB1 is most similar to early Homo. Third, we build a brain endocast classifier to show that LB1 is not within the normal range of variation in H. sapiens. These results combined support the hypothesis of a very early shared ancestor for LB1 and H. erectus, and illustrate how discriminant analysis approaches can be successfully used to help classify newly discovered specimens.

1D-LDA vs. 2D-LDA: When is vector-based linear discriminant analysis better than matrix-based?

Recent advances have shown that algorithms with (2D) matrix-based representation perform better than the traditional (1D) vector-based ones. In particular, 2D-LDA has been widely reported to outperform 1D-LDA. However, would the matrix-based linear discriminant analysis be always superior and when would 1D-LDA be better? In this paper, we investigate into these questions and have a comprehensive comparison between 1D-LDA and 2D-LDA in theory and in experiments. We analyze the heteroscedastic problem in 2D-LDA and formulate mathematical equalities to explore the relationship between 1D-LDA and 2D-LDA; then we point out potential problems in 2D-LDA. It is shown that 2D-LDA has eliminated the information contained in the covariance information between different local geometric structures, such as the rows or the columns, which is useful for discriminant feature extraction, whereas 1D-LDA could preserve such information. Interestingly, this new finding indicates that 1D-LDA is able to gain higher Fisher score than 2D-LDA in some extreme case. Furthermore, sufficient conditions on which 2D-LDA would be Bayes optimal for two-class classification problem are derived and comparison with 1D-LDA in this aspect is also analyzed. This could help understand how 2D-LDA is expected to achieve at its best, further discover its relationship with 1D-LDA, and well support other findings. After the theoretical analysis, comprehensive experimental results are reported by fairly and extensively comparing 1D-LDA with 2D-LDA. In contrast to the existing view that some 2D-LDA based algorithms would perform better than 1D-LDA when the number of training samples for each class is small or when the number of discriminant features used is small, we show that it is not always true and show that some standard 1D-LDA based algorithms could perform better in those cases on some challenging data sets.

Acoustic Feature Analysis and Discriminative Modeling of Filled Pauses for Spontaneous Speech Recognition

Most automatic speech recognizers (ASRs) concentrate on read speech, which is different from spontaneous speech with disfluencies. ASRs cannot deal with speech with a high rate of disfluencies such as filled pauses, repetitions, lengthening, repairs, false starts and silence pauses. In this paper, we focus on the feature analysis and modeling of the filled pauses "ah," "ung," "um," "em," and "hem" in spontaneous speech. Karhunen-Loeve transform (KLT) and linear discriminant analysis (LDA) were adopted to select discriminant features for filled pause detection. In order to suitably determine the number of discriminant features, Bartlett hypothesis testing was adopted. Twenty-six features were selected using Bartlett hypothesis testing. Gaussian mixture models (GMMs), trained with a gradient decent algorithm, were used to improve the filled pause detection performance. The experimental results show that the filled pause detection rates using KLT and LDA were 84.4% and 86.8%, respectively. A significant improvement was obtained in the filled pause detection rate using the discriminative GMM with KLT and LDA. In addition, the LDA features outperformed the KLT features in the detection of filled pauses.