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arXiv 1609.01423stat.ML
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基于TV-弹性网惩罚的结构稀疏主成分分析

Structured Sparse Principal Components Analysis with the TV-Elastic Net penalty

Amicie de Pierrefeu, Tommy Löfstedt, Fouad Hadj-Selem, Mathieu Dubois, Philippe Ciuciu, Vincent Frouin, Edouard Duchesnay

摘要:

主成分分析(PCA)是一种广泛用于数据分析的探索性工具,用于揭示群体内的主要变异模式。尽管它能够在低维空间中表示数据集,但PCA的可解释性仍然有限。然而,在神经影像学中,发现临床上可解释的表型标记物是至关重要的,这些标记物可以解释人群脑图像的主要变异性。最近,已经提出了标准PCA方法的一些替代方案,例如稀疏PCA,其目的是限制组件的密度。然而,稀疏性本身并不能完全解决可解释性问题,因为它可能产生分散和不稳定的成分。我们假设,有关数据结构的先验信息的结合可能会导致改善大脑模式的相关性和可解释性。因此,我们提出了一个简单的扩展流行的PCA框架,增加了结构化的稀疏性惩罚的加载向量,以确定在大脑图像中占大多数的变异性的几个稳定的区域。这种结构化稀疏性可以通过组合l1和总变差(TV)惩罚来获得,其中TV正则化对关于数据结构的高阶信息进行编码。本文提出了结构化稀疏PCA(表示为SPCA-TV)优化框架及其解决方案。我们证明了效率和多功能性的SPCA-TV三个不同的数据集。SPCA-TV相对于非结构化方法的收益是显著的,因为SPCA-TV以易于解释的可理解的大脑模式的形式揭示了数据集内的可变性,并且在不同的样本中更稳定。

英文摘要:

Principal component analysis (PCA) is an exploratory tool widely used in data analysis to uncover dominant patterns of variability within a population. Despite its ability to represent a data set in a low-dimensional space, the interpretability of PCA remains limited. However, in neuroimaging, it is essential to uncover clinically interpretable phenotypic markers that would account for the main variability in the brain images of a population. Recently, some alternatives to the standard PCA approach, such as Sparse PCA, have been proposed, their aim being to limit the density of the components. Nonetheless, sparsity alone does not entirely solve the interpretability problem, since it may yield scattered and unstable components. We hypothesized that the incorporation of prior information regarding the structure of the data may lead to improved relevance and interpretability of brain patterns. We therefore present a simple extension of the popular PCA framework that adds structured sparsity penalties on the loading vectors in order to identify the few stable regions in the brain images accounting for most of the variability. Such structured sparsity can be obtained by combining l1 and total variation (TV) penalties, where the TV regularization encodes higher order information about the structure of the data. This paper presents the structured sparse PCA (denoted SPCA-TV) optimization framework and its resolution. We demonstrate the efficiency and versatility of SPCA-TV on three different data sets. The gains of SPCA-TV over unstructured approaches are significant,since SPCA-TV reveals the variability within a data set in the form of intelligible brain patterns that are easy to interpret, and are more stable across different samples.

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