<scp>ChartNet</scp>: Reducing Subjectivity in Stock Prediction Through Unified Technical Chart Representation

ABSTRACT Technical analysis, which includes technical indicators and charts derived from specific rules, has proven effective and widely used for stock movement prediction. However, technical chart evaluation is often limited by subjectivity, arising from sparse chart types and substantial information loss due to rigid rules. While pattern recognition algorithms have been developed to address this issue, they still rely on manual chart labelling and primarily focus on closing prices, leaving much of the chart's broader information untapped. To overcome these limitations, we propose a novel framework called ChartNet, designed to extract general information from technical charts and reduce subjectivity in chart analysis. ChartNet employs a unified representation for charts across financial series with varying simplification levels and leverages a chart triplet loss function for unsupervised training, eliminating the need for labelled data. Compared with several state‐of‐the‐art baselines, our framework has reached the best prediction accuracy on CSI‐300, SZ‐50 components and Dow Jones Index in 2022: 65.91%, 63.70% and 64.96% respectively. In backtesting using actual stock data, our framework achieves the highest average return of 1.12 and 1.15. Furthermore, we highlight the interpretability of ChartNet through two case studies, some important charts and failure cases, illustrating its capability to uncover meaningful insights from charts. This research contributes to advancing the objective evaluation of technical charts and promoting a more comprehensive understanding of chart‐based stock prediction performance.