Description Usage Arguments Details Value Author(s) References See Also Examples
This is an internal function of package MortalitySmooth
which
creates equally-spaced B-splines basis over an abscissa of data within
the function Mort1Dsmooth
.
1 | MortSmooth_bbase(x, xl, xr, ndx, deg)
|
x |
vector for the abscissa of data. |
xl |
left boundary. |
xr |
right boundary. |
ndx |
number of internal knots minus one or number of internal intervals. |
deg |
degree of the splines. |
The function reproduce an algorithm presented by Eilers and Marx
(2010) using differences of truncated power functions (see
MortSmooth_tpower
). The final matrix has a single
B-spline for each of the [ndx
+ deg
] columns. The number
of rows is equal to the length of x
.
The function differs from bs
in the package splines
since it automatically constructed B-splines with identical
shape. This would allow a simple interpretation of coefficients and
application of simple differencing.
A matrix containing equally-spaced B-splines of degree deg
along x
for each column.
Carlo G Camarda
Eilers P. H. C. and B. D. Marx (2010). Splines, Knots, and Penalties. Wiley Interdisciplinary Reviews: Computational Statistics. 2, 637-653.
1 2 3 4 5 6 7 8 9 | x <- seq(0,1,length=500)
## B-splines basis of degree 1
B1 <- MortSmooth_bbase(x=x, xl=min(x), xr=max(x),
ndx=10, deg=1)
matplot(x, B1, t="l", main="B-splines basis of degree 1")
## B-splines basis of degree 3
B3 <- MortSmooth_bbase(x=x, xl=min(x), xr=max(x),
ndx=10, deg=3)
matplot(x, B3, t="l", main="B-splines basis of degree 3")
|
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