Struct rgsl::types::basis_spline::BSpLineWorkspace
source · pub struct BSpLineWorkspace { /* private fields */ }Implementations§
source§impl BSpLineWorkspace
impl BSpLineWorkspace
sourcepub fn new(k: usize, nbreak: usize) -> Option<BSpLineWorkspace>
pub fn new(k: usize, nbreak: usize) -> Option<BSpLineWorkspace>
This function allocates a workspace for computing B-splines of order k.
The number of breakpoints is given by nbreak. This leads to n = nbreak + k - 2 basis functions.
Cubic B-splines are specified by k = 4. The size of the workspace is O(5k + nbreak).
sourcepub fn knots(&mut self, breakpts: &VectorF64) -> Value
pub fn knots(&mut self, breakpts: &VectorF64) -> Value
This function computes the knots associated with the given breakpoints and stores them internally in w->knots.
sourcepub fn knots_uniform(&mut self, a: f64, b: f64) -> Value
pub fn knots_uniform(&mut self, a: f64, b: f64) -> Value
This function assumes uniformly spaced breakpoints on [a,b] and constructs the corresponding knot vector using the previously specified nbreak parameter. The knots are stored in w->knots.
sourcepub fn eval(&mut self, x: f64, B: &mut VectorF64) -> Value
pub fn eval(&mut self, x: f64, B: &mut VectorF64) -> Value
This function evaluates all B-spline basis functions at the position x and stores them in the vector B, so that the i-th element is B_i(x).
The vector B must be of length n = nbreak + k - 2. This value may also be obtained by calling gsl_bspline_ncoeffs.
Computing all the basis functions at once is more efficient than computing them individually, due to the nature of the defining recurrence relation.
sourcepub fn eval_non_zero(
&mut self,
x: f64,
Bk: &mut VectorF64,
istart: &mut usize,
iend: &mut usize
) -> Value
pub fn eval_non_zero(
&mut self,
x: f64,
Bk: &mut VectorF64,
istart: &mut usize,
iend: &mut usize
) -> Value
This function evaluates all potentially nonzero B-spline basis functions at the position x and stores them in the vector Bk, so that the i-th element is B_(istart+i)(x).
The last element of Bk is B_(iend)(x). The vector Bk must be of length k. By returning only the nonzero basis functions, this function allows quantities involving linear combinations of the B_i(x) to be computed without unnecessary terms (such linear combinations occur, for example, when evaluating an interpolated function).
sourcepub fn ncoeffs(&mut self) -> usize
pub fn ncoeffs(&mut self) -> usize
This function returns the number of B-spline coefficients given by n = nbreak + k - 2.
sourcepub fn greville_abscissa(&mut self, i: usize) -> f64
pub fn greville_abscissa(&mut self, i: usize) -> f64
The Greville abscissae are defined to be the mean location of k-1 consecutive knots in the knot vector for each basis spline function of order k.
With the first and last knots in the gsl_bspline_workspace knot vector excluded, there are gsl_bspline_ncoeffs Greville abscissae for any given B-spline basis.
These values are often used in B-spline collocation applications and may also be called Marsden-Schoenberg points.
Returns the location of the i-th Greville abscissa for the given B-spline basis. For the ill-defined case when k=1, the implementation chooses to return breakpoint interval midpoints.