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\name{regdistdiffone}
\alias{regdistdiffone}
%- Also NEED an `\alias' for EACH other topic documented here.
\title{Regression difference within reference group and between-group dissimilarities}
\description{
Given two dissimilarity matrices \code{dmx} and \code{dmy}, an indicator
vector \code{x} and a grouping, this computes the difference between
standard least squares regression predictions at point
\code{xcenterbetween}. The regressions are based on the dissimilarities
in \code{dmx} vs. \code{dmy} for objects indicated in
\code{x}. \code{grouping} indicates the two groups, and the difference
is computed between regressions based on (a) the within-group
distances of the reference group \code{rgroup} and (b) these together
with the between-group distances.
}
\usage{
regdistdiffone(x,dmx,dmy,grouping,xcenter=0,xcenterbetween=0,rgroup)
}
%- maybe also `usage' for other objects documented here.
\arguments{
\item{x}{vector of logicals of length of the number of objects on which
dissimilarities \code{dmx} and \code{dmy} are based.}
\item{dmx}{dissimilarity matrix or object of class
\code{\link{dist}}. Explanatory dissimilarities.}
\item{dmy}{dissimilarity matrix or object of class
\code{\link{dist}}. Response dissimilarities.}
\item{grouping}{vector of length of the number of objects on which
dissimilarities \code{dmx} and \code{dmy} are based. Grouping
vector. Regressions will be based on the first two values that
appear in \code{unique(grouping[x])} (note that objects that are not
assigned to one of these groups will be ignored); normally
\code{grouping} should indicate only
two groups on the objects with \code{x=TRUE}, and then these are used.}
\item{xcenter}{numeric. Dissimilarities \code{dmx} are centered by
this, i.e., this value is subtracted from the dissimilarities before
regression.}
\item{xcenterbetween}{numeric. This specifies the x- (dissimilarity)
value at which predictions from the two regressions are
compared. Note that this is interpreted as after centering by
\code{xcenter}.}
\item{rgroup}{one of the values of \code{grouping}, specifying the
reference group.}
}
\value{
Difference between
standard least squares regression predictions for the two regressions at point
\code{xcenterbetween}.
}
\references{
Hausdorf, B. and Hennig, C. (2019) Species delimitation and
geography. Submitted.
}
\seealso{
\code{\link{regdistbetweenone}}
}
\author{Christian Hennig
\email{christian.hennig@unibo.it}
\url{https://www.unibo.it/sitoweb/christian.hennig/en}}
\examples{
options(digits=4)
data(veronica)
ver.geo <- coord2dist(coordmatrix=veronica.coord[173:207,],
file.format="decimal2")
vei <- prabinit(prabmatrix=veronica[173:207,],distance="jaccard")
species <-c(rep(1,13),rep(2,22))
regdistdiffone(rep(TRUE,35),ver.geo,vei$distmat,grouping=species,
xcenter=0,xcenterbetween=100,rgroup=2)
}
\keyword{regression}% __ONLY ONE__ keyword per line
\keyword{spatial}% __ONLY ONE__ keyword per line
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