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The interpolation function for a given dataset is stored in a
`gsl_interp2d`

object. These are created by the following functions.

- Function:
*gsl_interp2d ****gsl_interp2d_alloc***(const gsl_interp2d_type **`T`, const size_t`xsize`, const size_t`ysize`) -
This function returns a pointer to a newly allocated interpolation object of type

`T`for`xsize`grid points in the*x*direction and`ysize`grid points in the*y*direction.

- Function:
*int***gsl_interp2d_init***(gsl_interp2d **`interp`, const double`xa`[], const double`ya`[], const double`za`[], const size_t`xsize`, const size_t`ysize`) This function initializes the interpolation object

`interp`for the data (`xa`,`ya`,`za`) where`xa`and`ya`are arrays of the*x*and*y*grid points of size`xsize`and`ysize`respectively, and`za`is an array of function values of size`xsize`*`ysize`. The interpolation object (`gsl_interp2d`

) does not save the data arrays`xa`,`ya`, and`za`and only stores the static state computed from the data. The`xa`and`ya`data arrays are always assumed to be strictly ordered, with increasing*x,y*values; the behavior for other arrangements is not defined.

- Function:
*void***gsl_interp2d_free***(gsl_interp2d **`interp`) This function frees the interpolation object

`interp`.