Numerical verification of the orders of accuracy of truncated asymptotic expansion solutions to the van der Pol equation

We propose a numerical method to verify the orders of accuracy of truncated asymptotic expansion solutions to the van der Pol equation. Our proposed method is simpler than an existing method (Deeba and Xie in J Comput Anal Appl 3(2): 165–171, 2001). Our proposed method does not need any technique of a least-squares fit of error data, whereas the existing one does. Numerical simulations confirm that our proposed method works effectively.