Structured variable selection in support vector machines

When applying the support vector machine (SVM) to high-dimensional classification problems, we often impose a sparse structure in the SVM to eliminate the influences of the irrelevant predictors. The lasso and other variable selection techniques have been successfully used in the SVM to perform automatic variable selection. In some problems, there is a natural hierarchical structure among the variables. Thus, in order to have an interpretable SVM classifier, it is important to respect the heredity principle when enforcing the sparsity in the SVM. Many variable selection methods, however, do not respect the heredity principle. In this paper we enforce both sparsity and the heredity principle in the SVM by using the so-called structured variable selection (SVS) framework originally proposed in Yuan, Joseph and Zou (2007). We minimize the empirical hinge loss under a set of linear inequality constraints and a lasso-type penalty. The solution always obeys the desired heredity principle and enjoys sparsity. The new SVM classifier can be efficiently fitted, because the optimization problem is a linear program. Another contribution of this work is to present a nonparametric extension of the SVS framework, and we propose nonparametric heredity SVMs. Simulated and real data are used to illustrate the merits of the proposed method.Comment: Published in at http://dx.doi.org/10.1214/07-EJS125 the Electronic Journal of Statistics (http://www.i-journals.org/ejs/) by the Institute of Mathematical Statistics (http://www.imstat.org

The Relationship Between Physical Exercise and Mobile Phone Addiction of College Students from Low Social Classes

Mobile phone addiction has become a common phenomenon among college students, which seriously affects their physical and mental health. In this process, individuals with a strong sense of loneliness tend to seek social support and belonging in the virtual network, which leads to the occurrence of mobile phone addiction. At the same time, studies have begun to explore ways to reduce mobile phone addiction by improving physical activity. The purpose of this study was to explore the impact of low-level college students\u27 physical exercise on mobile phone addiction, and focuses on the mediating mechanism of loneliness. The mobile phone addiction scale, the physical activity level scale, and the loneliness scale were selected as the subjects. SPSS 23.0 was used to perform descriptive statistics, correlation analysis, multiple regression analysis, and bootstrap mediation effect test on the data. There were significant differences in gender dimensions between physical exercise, mobile phone addiction, and loneliness of low-level college students. Correlation analysis shows that there is a significant negative correlation between physical exercise and mobile phone addiction (r = -0.14, P \u3c 0.01) and loneliness (r = -0.15, P \u3c 0.01). Loneliness and mobile phone addiction (r = 0.29, P \u3c 0.01) was significantly positively correlated. The test results of the mediating effect show that the 95% confidence interval of the indirect effect Bootstrap produced by loneliness does not contain a value of 0, indicating that loneliness has a significant mediating effect between the level of physical exercise and mobile phone addiction (standardized effect value = -0.58, Accounted for 29% of the total effect). The level of physical exercise of low-level college students is significantly negatively related to mobile phone addiction and loneliness, and loneliness is significantly positively related to mobile phone addiction. There is a mediating effect of loneliness between physical exercise and mobile phone addiction

College Students’ Time Management Disposition, Self-Esteem and Mobile Phone Addiction: A Moderate Mediation Model

The purpose of this study was to analyze the impact of time management disposition on mobile phone addiction, explore the mediating role of self-esteem, and examine the differences between active and inactive college students in this mediating role. 887 college students participated in this study with valid measures. According to physical activity rating scale (PARS-3), students who met the recommendations of the World Health Organization\u27s Global recommendations on physical activity for health were categorized into active groups while the others were inactive group. The data was subjected to mediation model testing and multi-group comparison using Amos 21.0. The proportion of physical inactivity of college students was as high as 66.76%, there were significant differences between active and inactive college student in time monitoring concept, time efficacy, self-esteem, withdrawal symptoms, prominent behavior, social comfort and mood change. Each dimension of time management disposition was significantly negatively correlated with each dimension of mobile phone addiction, and was significantly positively correlated with self-esteem. Self-esteem was significantly negatively correlated with all dimensions of mobile phone addiction. According to the model test, the data fitted the hypothesized model well. In the whole sample model and active group model, self-esteem played a partial mediating role. In the inactive college student group, the exercise value cognition played a part of mediating role. Multi-group analysis found that the moderating effect of active or not was not significant. Self-esteem played a part of mediating role in the influence of time management disposition on mobile phone addiction. The findings suggest that persistent participation in physical activity help students to improve time management ability and reduce mobile phone dependence and even addiction. Future research needs to explore more influential factors for promoting college students\u27 physical and mental health

Relationship Between Procrastination and Exercise Behavior Among College Students: The Mediating Effects of Time Efficiency

Procrastination is prevalent in the study and life of the college student population. There is evidence suggesting that procrastination can have a negative impact on mood and behavior. However, in the field of exercise, the effects and mechanisms of procrastination on exercise have not been widely studied. Therefore, this study investigates the relationship between procrastination and exercise volume of college students, and discusses the mediation effect of time efficiency. The sample comprised 910 university students from 5 provinces（female: 509, male: 401）who completed inventories assessing their procrastination, time efficiency and exercise volume, and the relationships between these variables were examined using a model of mediation. In the present study, the appropriate IRB approval has been obtained from East China Normal University. There are significant differences in procrastination (t = 2.43, p \u3c 0.05) and exercise volume (t = 7.42, p \u3c 0.01) among college students of different genders and no difference in the sense of time efficiency. The body mass index is classified as lean (BMI \u3c 18.5), normal (18.5 ≤ BMI ≤ 23.9), overweight (24.0 ≤ BMI ≤ 27.9) and obese (BMI ≥ 28) by standard, and there are significant differences between body mass index and exercise volume (F = 7.51, p \u3c 0.01). Procrastination was negatively correlated with time efficiency (r = -0.525, p \u3c 0.01) and exercise volume (r = -0.159, p \u3c 0.01), and there was a significant positive correlation between time efficiency and exercise volume (r = 0.164, p \u3c 0.01). Mediating effect test shows that the time efficiency has a certain intermediary effect between procrastination and exercise volume (indirect effect = -0.090, LLCI = -0.163, ULCI = -0.012). Findings provide support that procrastination affects college students\u27 physical exercise through time efficiency. We can start with improving college students\u27 time efficiency to promote the participation of physical activities. Future research needs more attention to overweight and obese college students