I. Introduction
Forecasting stock prices is of significant importance for analyzing financial systems, as the stock market reflects the economic situation of a country, even the world. Accurate prediction of the stock market allows investors and other stakeholders to understand the movement of the financial market. Effective trading strategies are then adopted to achieve greater profits as well as returns with less risk [1]. In general, the stock market is often analyzed by researchers as a complex system [2]–[4]. However, the non-linearity, high noise and volatility of the stock market make the prediction of financial systems take higher risks than to other complex systems [5]. In addition, external factors such as national macro adjustments, changes from the political situation and investor psychology make the prediction of the financial system extremely difficult [6], [7]. Data-driven methods show great potential for the analysis and control of such complex systems [8], [9].