Function rgsl::interpolation::eval_deriv2

pub fn eval_deriv2(interp: &Interp, xa: &[f64], ya: &[f64], x: f64, acc: &mut InterpAccel) -> f64

This function returns 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.