Struct CubicSpline 

pub struct CubicSpline<T: Float> { /* private fields */ }

Cubic spline 1-D interpolator.

Precomputes polynomial coefficients for each segment at construction time. Each evaluation is O(log n) via binary search.

Implementations

impl<T: Float> CubicSpline<T>

pub fn new( xs: &[T], ys: &[T], boundary: SplineBoundary<T>, extrap: Extrapolate, ) -> Result<Self>

Construct a cubic spline interpolator.

Errors

• xs and ys must have the same length (>= 3).
• xs must be strictly increasing.
• All values must be finite.

Examples

let xs = [0.0_f64, 1.0, 2.0, 3.0];
let ys = [0.0, 1.0, 4.0, 9.0]; // roughly x²
let spline = CubicSpline::new(&xs, &ys, SplineBoundary::Natural, Extrapolate::Error).unwrap();
let y = spline.eval(1.5).unwrap();
assert!((y - 2.25).abs() < 0.5); // close to 1.5²

pub fn eval(&self, x: T) -> Result<T>

Evaluate the spline at a single point.

Examples

let spline = CubicSpline::new(
    &[0.0_f64, 1.0, 2.0, 3.0], &[0.0, 1.0, 4.0, 9.0],
    SplineBoundary::Natural, Extrapolate::Error,
).unwrap();
let y = spline.eval(1.5).unwrap();
assert!((y - 2.25).abs() < 0.5);

pub fn eval_many(&self, xs: &[T]) -> Result<Vec<T>>

Evaluate at many points.

Examples

let spline = CubicSpline::new(
    &[0.0_f64, 1.0, 2.0, 3.0], &[0.0, 1.0, 4.0, 9.0],
    SplineBoundary::Natural, Extrapolate::Error,
).unwrap();
let ys = spline.eval_many(&[0.5, 1.5, 2.5]).unwrap();
assert_eq!(ys.len(), 3);

pub fn derivative(&self, x: T) -> Result<T>

Evaluate the first derivative at a single point.

Examples

let spline = CubicSpline::new(
    &[0.0_f64, 1.0, 2.0, 3.0], &[0.0, 1.0, 4.0, 9.0],
    SplineBoundary::Natural, Extrapolate::Error,
).unwrap();
let dy = spline.derivative(1.0).unwrap();
assert!(dy > 0.0); // increasing function

pub fn second_derivative(&self, x: T) -> Result<T>

Evaluate the second derivative at a single point.

Examples

let spline = CubicSpline::new(
    &[0.0_f64, 1.0, 2.0, 3.0], &[0.0, 1.0, 4.0, 9.0],
    SplineBoundary::Natural, Extrapolate::Error,
).unwrap();
let d2y = spline.second_derivative(0.0).unwrap();
// Natural boundary: second derivative = 0 at endpoints
assert!(d2y.abs() < 1e-10);

Trait Implementations

impl<T: Clone + Float> Clone for CubicSpline<T>

fn clone(&self) -> CubicSpline<T>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug + Float> Debug for CubicSpline<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.