\name{bookstein2d}
\alias{bookstein2d}
\title{Bookstein's baseline registration for 2D data}
\description{Carries out Bookstein's baseline registration and
calculates a mean shape.  } 
\usage{bookstein2d(A,l1=1,l2=2)}
\arguments{
\item{A}{a k x 2 x n real array, or k x n complex matrix, where 
    k is the number of landmarks, n is the number of observations} 
\item{l1}{an integer : l1 is sent to (-1/2,0) in the registration} 
\item{l2}{an integer : l2 is sent to (1/2,0) in the registration}
}
\value{ 
   A list with components 
\item{k}{no of landmarks}
\item{n}{sample size}
\item{mshape}{Bookstein mean shape with baseline l1, l2} 
\item{bshpv}{the k x n x 2 array of Bookstein shape variables, including 
the baseline} 
}
\references{Dryden, I.L. and Mardia, K.V. (1998) 
Statistical Shape Analysis. Wiley, Chichester. 
Chapter 2. 

Bookstein, F. L. (1986) Size and shape spaces for landmark data in two dimensions 
(with discussion). Statistical Science, 1:181-242. 
} 
\author{Ian Dryden}

\examples{
data(gorf.dat)
data(gorm.dat)

bookf<-bookstein2d(gorf.dat)
bookm<-bookstein2d(gorm.dat)

plotshapes(bookf$mshape,bookm$mshape,joinline=c(1,6,7,8,2,3,4,5,1))
}

\keyword{multivariate}