Rakib Mahmudul Islam, Nobi Ashadun, Lee Jae Woo
Department of Computer Science and Telecommunication Engineering, Noakhali Science and Technology University, Sonapur, Noakhali, 3814, Bangladesh.
Department of Physics, Inha University, Incheon, Republic of Korea.
Sci Rep. 2021 Sep 2;11(1):17618. doi: 10.1038/s41598-021-97100-1.
Much research has been done on time series of financial market in last two decades using linear and non-linear correlation of the returns of stocks. In this paper, we design a method of network reconstruction for the financial market by using the insights from machine learning tool. To do so, we analyze the time series of financial indices of S&P 500 around some financial crises from 1998 to 2012 by using feature ranking approach where we use the returns of stocks in a certain day to predict the feature ranks of the next day. We use two different feature ranking approaches-Random Forest and Gradient Boosting-to rank the importance of each node for predicting the returns of each other node, which produces the feature ranking matrix. To construct threshold network, we assign a threshold which is equal to mean of the feature ranking matrix. The dynamics of network topology in threshold networks constructed by new approach can identify the financial crises covered by the monitored time series. We observe that the most influential companies during global financial crisis were in the sector of energy and financial services while during European debt crisis, the companies are in the communication services. The Shannon entropy is calculated from the feature ranking which is seen to increase over time before market crash. The rise of entropy implies the influences of stocks to each other are becoming equal, can be used as a precursor of market crash. The technique of feature ranking can be an alternative way to infer more accurate network structure for financial market than existing methods, can be used for the development of the market.
在过去二十年里,人们利用股票回报的线性和非线性相关性,对金融市场的时间序列进行了大量研究。在本文中,我们借鉴机器学习工具的见解,设计了一种金融市场网络重构方法。为此,我们采用特征排序方法,分析了1998年至2012年期间一些金融危机前后标准普尔500指数的金融时间序列,其中我们使用某一天的股票回报来预测下一天的特征排名。我们使用两种不同的特征排序方法——随机森林和梯度提升——来对每个节点预测其他节点回报的重要性进行排名,从而生成特征排名矩阵。为了构建阈值网络,我们设定一个等于特征排名矩阵均值的阈值。通过新方法构建的阈值网络中的网络拓扑动态,可以识别被监测时间序列所涵盖的金融危机。我们观察到,全球金融危机期间最具影响力的公司来自能源和金融服务领域,而在欧洲债务危机期间,这些公司则来自通信服务领域。从特征排名中计算出的香农熵在市场崩溃前随时间增加。熵的增加意味着股票之间的相互影响正变得均等,可被用作市场崩溃的先兆。与现有方法相比,特征排序技术可以作为一种推断金融市场更准确网络结构的替代方法,可用于市场发展。