bspline {ibs}

B-spline function

Description

Evaluate the value of the B-spline function with knots knots, order ord, and coefficients coef at value(s) x.

Usage

bspline(x, knots, ord, coef = rep(1, length(knots) - ord))

Arguments

x

Numerical value or vector. The value(s) at which to evaluate the B-spline.

knots

Numerical vector. The knot positions/sites of the B-spline function.

ord

An integer >=1. The order of the B-spline function. Equals degree plus 1.

coef

A numerical vector. The coefficients (de Boor points) defining the B-spline function.

Value

A scalar or a vector of length equal to that of x.

Note

In contrast to the implementation based on the splineDesign function from the splines package, this version of the B-spline function is left-continuous at the rightmost knot site.

Author(s)

Feng Chen <[e-mail]>

References

de Boor, C. (2001) A Practical Guide to Splines. Revised Edition. Springer: New York.

See Also

splineDesign

Examples

kns <- c(rep(0,4),1:4*0.2,rep(1,4))
bspline(0:10/10,kns,3,rep(1,length(kns)-3))
splines::splineDesign(kns,0:10/10,3)%*%rep(1,length(kns)-3)