  Although the isogeometric collocation (IGA-C) method has been successfully
utilized in practical applications due to its simplicity and efficiency, only a
little theoretical results have been established on the numerical analysis of
the IGA-C method. In this paper, we deduce the convergence rate of the
consistency of the IGA-C method. Moreover, based on the formula of the
convergence rate, the necessary and sufficient condition for the consistency of
the IGA-C method is developed. These results advance the numerical analysis of
the IGA-C method.
