Function approx1_v2 

pub fn approx1_v2<T, P>(
    output: &mut Array<T>,
    input: &Array<T>,
    pos: &Array<P>,
    method: InterpType,
    off_grid: f32,
)
where
    T: HasAfEnum + FloatingPoint,
    P: HasAfEnum + RealFloating,

Same as approx1 but uses existing Array as output