B.Iso {addreg}  R Documentation 
Function used in the definition of smooth terms within addreg.smooth
model formulae. The function does not evaluate a smooth — it exists purely to help
set up a model using smooths.
B(..., knots = NULL, knot.range = 0:5)
Iso(...)
... 
variable that this smooth is a function of. Note that unlike 
knots 
unique positions of interior knots of a Bspline basis. Boundary knots are created automatically. 
knot.range 
if At least one of 
The function does not evaluate the variable arguments; the output from this function is used when producing the model matrix, at which point the actual basis functions are constructed.
B
is used to specify an order3 Bspline basis (which can be
restricted to be monotonically nondecreasing via the
mono
argument in addreg.smooth
). If
length(knot.range) > 1
, models with each of the
specified number of interior knots will be fit, and the model
with the best (smallest) aic.c
will be returned.
Iso
is used to specify an isotonic basis, designed
such that the resulting function has nonnegative
increments at each observed covariate value. When
Iso
is used, the resulting function will always be
monotonically nondecreasing, regardless of the value of
mono
.
An object of class "B.smooth"
(for B
) or
"Iso.smooth"
(for Iso
), which is a list with
the following elements:
term 
name of the term
provided in the 
termlabel 
label for the term in the model; e.g. for
term 
knots 
vector of interior knots (if
specified). 
knot.range 
vector of number of interior knots.

Mark W. Donoghoe markdonoghoe@gmail.com
s
performs a similar function in the mgcv
package.
## See example(addreg.smooth) for an example of specifying smooths in model
## formulae.