% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/lfebd3.R
\name{build_triplet}
\alias{build_triplet}
\title{Build recursive triplets for fractional or confounded reduction}
\usage{
build_triplet(mat, type = c("fractional", "confounded"))
}
\arguments{
\item{mat}{Matrix to be partitioned and reduced.}

\item{type}{Character string specifying the reduction rule. Must be one of
`"fractional"` or `"confounded"`.}
}
\value{
A list of three matrices, conventionally interpreted as `P1`, `P2`,
  and `P3`.
}
\description{
Recursively partitions a design matrix into three components and returns
three reduced patterns used in the fractional and confounded selection
rules.
}
\details{
For 9-row base cases, the selection rule differs by `type`.
Fractional reduction uses consecutive row groups, whereas confounded
reduction uses interleaved row groups. Larger matrices are handled
recursively.
}
\seealso{
[reduce_once()], [reduce_repeated()]
}
\keyword{internal}
