The interpolation function for a given dataset is stored in a
gsl_interp object. These are created by the following functions.
This function initializes the interpolation object interp for the data (xa,ya) where xa and ya are arrays of size size. The interpolation object (
gsl_interp) does not save the data arrays xa and ya and only stores the static state computed from the data. The xa data array is always assumed to be strictly ordered, with increasing x values; the behavior for other arrangements is not defined.
This function frees the interpolation object interp.