Transfer learning for nonparametric regression is considered. We first study the non-asymptotic minimax risk for this problem and develop a novel estimator called the confidence thresholding estimator, which is shown to achieve the minimax optimal risk up to a logarithmic factor. Our results demonstrate two unique phenomena in transfer learning: auto-smoothing and super-acceleration, which differentiate it from nonparametric regression in a traditional setting. We then propose a data-driven algorithm that adaptively achieves the minimax risk up to a logarithmic factor across a wide range of parameter spaces. Simulation studies are conducted to evaluate the numerical performance of the adaptive transfer learning algorithm, and a real-world example is provided to demonstrate the benefits of the proposed method.

非参数回归的传递学习研究中，开发了一种自信阈值估计器，该估计器被证明在寻找最小最大风险时能够实现对数因子的最优性。结果展示了传递学习中的两个独特现象：自动平滑和超加速，这两者使之与传统环境下的非参数回归有所区别。随后，提出了一种数据驱动算法，能够自适应地在广泛的参数空间内达到对数因子的最小最大风险。通过模拟研究来评估自适应传递学习算法的数值性能，并提供了一个实际例子以演示所提方法的好处。

非参数回归的迁移学习：非渐近极小化分析与自适应程序