cppBASptsIndexed {spbal}

Generate numbers from a Halton Sequence along a specified set of indices.

Description

For efficiency, this function can generate points along a random start Halton Sequence for a predefined set of indices away from the seed. When boxes are provided it will calculate the Halton Sequence only at those boxes and not along the entire sequence.

Usage

cppBASptsIndexed(
  n = 10L,
  seeds = as.integer(c()),
  bases = as.numeric(c()),
  boxes = as.integer(c()),
  verbose = FALSE
)

Arguments

n

Number of points required.

seeds

Random starting point in each dimension.

bases

Co-prime base for the Halton Sequence.

boxes

Integer vector of indices to sample along the Halton sequence (default 1:n).

verbose

A boolean indicating whether informational messages are to be issued.

Details

When not all points along the Halton sequence are required, this function efficiently generates the points that are needed along a sequence. Taking all points from the random seed equates to boxes = 1:n. However, taking advantage of how the Halton Sequence repeats itself by B = prod(base^J), where $J$ is an integer. We can also select every Bth box to efficiently generate values at specific locations along the sequence. This reduces future computation when bounding boxes are large in comparison to the polygon being sampled.

Value

Matrix with the columns, order of points, x in [0,1) and y in [0,1)

Author(s)

Phil Davies, Paul van Dam-Bates, Blair Robertson.

Examples

# First 10 points in the Halton Sequence for base 2,3
spbal::cppBASptsIndexed(n = 10)
# First 10 points in the Halton Sequence for base 2,3 with
# starting point at the 15th and 22nd index.
spbal::cppBASptsIndexed(n = 10, seeds = c(14, 21))