用锚点样本增强少数类生成,提升不平衡表格数据分类效果
Anchor-based oversampling for imbalanced tabular data via contrastive and adversarial learning
- 基于边界锚点样本构建先验模型,指导生成与对抗学习
- 在16个真实数据集上,多数指标优于主流方法,尤其提升少数类召回率
- 适合医疗、安全等少数类关键的不平衡数据场景
不平衡数据指某一类别(多数类)出现频率远高于另一类别(少数类),常见于安全、医疗和人类活动等领域。传统分类算法易偏向多数类,导致少数类样本被误判,造成虚假高准确率。本文提出一种基于边界锚点样本的框架,首先利用锚点样本训练多层感知机(MLP)作为先验知识模型,辅助后续对抗与对比学习。设计新型深度生成模型 Anch-SCGAN,包含针对少数类和多数类的双生成器,以及融合预训练特征提取器的判别器。为提升生成器训练稳定性,引入基于重处理锚点样本的对比损失函数,并采用评分策略稳定对抗训练。通过锚点样本微调生成结果,提高样本精确度。在16个真实世界不平衡数据集上的实验表明,Anch-SCGAN 在多数评价指标上超越现有先进方法。
原文摘要 · Abstract (English)
Imbalanced data represent a distribution with more frequencies of one class (majority) than the other (minority). This phenomenon occurs across various domains, such as security, medical care and human activity. In imbalanced learning, classification algorithms are typically inclined to classify the majority class accurately, resulting in artificially high accuracy rates. As a result, many minority samples are mistakenly labelled as majority-class instances, resulting in a bias that benefits the majority class. This study presents a framework based on boundary anchor samples to tackle the imbalance learning challenge. First, we select and use anchor samples to train a multilayer perceptron (MLP) classifier, which acts as a prior knowledge model and aids the adversarial and contrastive learning procedures. Then, we designed a novel deep generative model called Anchor Stabilized Conditional Generative Adversarial Network or Anch-SCGAN in short. Anch-SCGAN is supported with two generators for the minority and majority classes and a discriminator incorporating additional class-specific information from the pre-trained feature extractor MLP. In addition, we facilitate the generator's training procedure in two ways. First, we define a new generator loss function based on reprocessed anchor samples and contrastive learning. Second, we apply a scoring strategy to stabilize the adversarial training part in generators. We train Anch-SCGAN and further finetune it with anchor samples to improve the precision of the generated samples. Our experiments on 16 real-world imbalanced datasets illustrate that Anch-SCGAN outperforms the renowned methods in imbalanced learning.
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