### 28.5 1D Evaluation of Interpolating Functions

Function: double gsl_interp_eval (const gsl_interp * interp, const double xa[], const double ya[], double x, gsl_interp_accel * acc)
Function: int gsl_interp_eval_e (const gsl_interp * interp, const double xa[], const double ya[], double x, gsl_interp_accel * acc, double * y)

  These functions return the interpolated value of y for a given point x, using the interpolation object interp, data arrays xa and ya and the accelerator acc. When x is outside the range of xa, the error code `GSL_EDOM` is returned with a value of `GSL_NAN` for y.

Function: double gsl_interp_eval_deriv (const gsl_interp * interp, const double xa[], const double ya[], double x, gsl_interp_accel * acc)
Function: int gsl_interp_eval_deriv_e (const gsl_interp * interp, const double xa[], const double ya[], double x, gsl_interp_accel * acc, double * d)

  These functions return the derivative d of an interpolated function for a given point x, using the interpolation object interp, data arrays xa and ya and the accelerator acc.

Function: double gsl_interp_eval_deriv2 (const gsl_interp * interp, const double xa[], const double ya[], double x, gsl_interp_accel * acc)
Function: int gsl_interp_eval_deriv2_e (const gsl_interp * interp, const double xa[], const double ya[], double x, gsl_interp_accel * acc, double * d2)

  These functions return the second derivative d2 of an interpolated function for a given point x, using the interpolation object interp, data arrays xa and ya and the accelerator acc.

Function: double gsl_interp_eval_integ (const gsl_interp * interp, const double xa[], const double ya[], double a, double b, gsl_interp_accel * acc)
Function: int gsl_interp_eval_integ_e (const gsl_interp * interp, const double xa[], const double ya[], double a, double b, gsl_interp_accel * acc, double * result)

  These functions return the numerical integral result of an interpolated function over the range [a, b], using the interpolation object interp, data arrays xa and ya and the accelerator acc.