Indefinite integral of B-spline
ibsp(f, const = 0, nint = 1L)
Function calculating requested integral
Function, B-spline such as returned by smbsp()
or par2bsp()
Numeric scalar or vector of length ncol(qw)
where
qw is weight matrix of f. Defines starting value of weights for indefinite
integral (0 by default).
Integer scalar >= 0, defines how many times to take integral (1 by default)
If f is B-spline, then following identity is held: dbsp(ibsp(f)) is identical to f. Generally, it does not work in the other sens: ibsp(dbsp(f)) is not f but not very far. If we can get an appropriate constant C=f(min(x)) then we can assert that ibsp(dbsp(f), const=C) is the same as f.