MakeGrid: Make a grid of x-values between domain knots

In gps: General P-Splines

Make a grid of x-values between domain knots

Description

Place equidistant grid points on each knot span to produce a grid of x-values between domain knots, suitable for evaluating B-splines.

Usage

MakeGrid(xd, n, rm.dup = FALSE)

Arguments

xd	domain knot sequence.
n	number of equidistant grid points on each knot span.
rm.dup	if FALSE, interior knots will appear twice on the grid; if TRUE, they will appear only once.

Details

Denote the domain knot sequence by s_0, s_1, s_2, \ldots, s_k, s_{k + 1}, where (s_j)_1^k are interior knots and s_0 = a, s_{k + 1} = b are domain endpoints. A knot span is the interval between two successive knots, i.e., [s_j, s_{j + 1}].

To make a suitable grid on [a, b] for evaluating B-splines, we can place n equidistant grid points on each knot span, ending up with n(k + 1) grid points in total. Interior knots will show up twice in this grid. To keep only one instance, set rm.dup = TRUE.

Value

A vector of grid points.

Author(s)

Zheyuan Li [e-mail]

Examples

require(gps)

## 4 domain knots: two interior knots 0.5 and 1.5 in domain [0, 3]
xd <- c(0, 0.5, 1.5, 3)

## interior knots will appear twice
MakeGrid(xd, 5, rm.dup = FALSE)

## interior knots only appear once
MakeGrid(xd, 5, rm.dup = TRUE)

gps documentation built on Nov. 2, 2023, 6:08 p.m.