basis_bs: Creating B-spline Basis Functions
In yixuan/fdaplus: Enhancement of the 'fda' package for functional data analysis

Description Usage Arguments Details Value Author(s)

This function constructs a bspline+ object that represents a series of B-spline basis functions.

1 2	basis_bs(range = c(0, 1), nbasis = NULL, order = 4, breaks = NULL, dropind = NULL)

`range`	A length-two numeric vector to define the interval on which basis functions can be evaluated. Default is `c(0, 1)`.
`nbasis`	The total number of basis functions, including the ones that need to be dropped. See section Details.
`order`	The order of the B-spline functions, which is the degree of splines plus one. Default is 4, standing for cubic splines.
`breaks`	A vector of break points (inner knots) to define the B-spline basis. This does not include the end points, which are defined by the parameter `range`. See section Details.
`dropind`	Indices of basis functions that need to be dropped. Default is `NULL`, meaning no basis will be dropped.

nbasis, order and breaks are related to each other, satisfying the condition nbasis == order + length(breaks). Hence when any one of nbasis and breaks is properly specified, the other one can be computed accordingly. For details,

If both nbasis and breaks are NULL (the default), nbasis will be set to order and there is no inner knot.
If nbasis is NULL and breaks is given, then nbasis will be calculated using the equation above.
If nbasis is given and breaks unspecified, a series of equally spaced inner knots will be calculated.
If both nbasis and breaks are provided, then the program will check their validity.