Nonparametric Estimation of Volatility Function with Variable Bandwidth Parameter

In this article, we introduce a new method for the volatility function estimation of continuous-time diffusion process dXt = μ(X t)dt + σ(X t)dWt, which is based on combining the idea of local linear smoother and variable bandwidth. We give the expressions for the conditional MSE and MISE of the estimator and obtain the optimal variable bandwidth. An explicit formula for the optimal variable bandwidth is presented by minimizing the MISE, which extends the related results in Fan and Gijbels (1992), etc. Finally, some simulations show that the performance of the proposed estimator with optimal variable bandwidth is often much better than that of the local linear estimator with invariable bandwidth. © 2013 Taylor and Francis Group, LLC.