Machine learning methods have recently seen a growing number of applications in financial trading. Being able to automatically extract patterns from past price data and consistently apply them in the future has been the focus of many quantitative trading applications. However, developing machine learning-based methods for financial trading is not straightforward, requiring carefully designed targets/rewards, hyperparameter fine-tuning, and so on. Furthermore, most of the existing methods are unable to effectively exploit the information available across various financial instruments. In this article, we propose a deep reinforcement learning-based approach, which ensures that consistent rewards are provided to the trading agent, mitigating the noisy nature of profit-and-loss rewards that are usually used. To this end, we employ a novel price trailing-based reward shaping approach, significantly improving the performance of the agent in terms of profit, Sharpe ratio, and maximum drawdown. Furthermore, we carefully designed a data preprocessing method that allows for training the agent on different FOREX currency pairs, providing a way for developing market-wide RL agents and allowing, at the same time, to exploit more powerful recurrent deep learning models without the risk of overfitting. The ability of the proposed methods to improve various performance metrics is demonstrated using a challenging large-scale data set, containing 28 instruments, provided by Speedlab AG.

Forecasting the movements of stock prices is one the most challenging problems in financial markets analysis. In this paper, we use Machine Learning (ML) algorithms for the prediction of future price movements using limit order book data. Two different sets of features are combined and evaluated: handcrafted features based on the raw order book data and features extracted by ML algorithms, resulting in feature vectors with highly variant dimensionalities. Three classifiers are evaluated using combinations of these sets of features on two different evaluation setups and three prediction scenarios. Even though the large scale and high frequency nature of the limit order book poses several challenges, the scope of the conducted experiments and the significance of the experimental results indicate that Machine Learning highly befits this task carving the path towards future research in this field.