CODE:

fixed.angle<-function(A,art.pt=NULL,angle.pts=NULL,rot.pts=NULL,angle=0){
if (length(dim(A))!=3){
stop(“Data matrix 1 not a 3D array (see ‘arrayspecs’).”) }
if(length(grep(“-999”,A))!=0){
stop(“Data matrix 1 contains missing values. Estimate these first(see ‘estimate.missing’).”) }
n<-dim(A)[3]; k<-dim(A)[2]; p<-dim(A)[1]
if (k!=2){
stop(“Method presently implemented for two-dimensional data only.”)}
if (angle>pi*2){
stop(“Additional angle must be specified in radians.”)}
if (angle< -pi*2){
stop(“Additional angle must be specified in radians.”)}
angl<-array(NA,dim=n)
for (i in 1:n){
A[,,i]<-t(t(A[,,i])-A[art.pt,,i])
angl[i]<- acos((A[angle.pts[1],,i]/sqrt(sum(A[angle.pts[1],,i]^2)))%*%(A[angle.pts[2],,i]/sqrt(sum(A[angle.pts[2],,i]^2))))
}
dev.angle<- (angl-mean(angl))+angle
if(A[angle.pts[1],1,1]<0){dev.angle<- -1*dev.angle}
for (i in 1:n){
r = matrix(c(cos(dev.angle[i]),-sin(dev.angle[i]),sin(dev.angle[i]),cos(dev.angle[i])),2)
A[rot.pts,,i] = A[rot.pts,,i]%*%r
}
return(A)
}