"factor.rotate" <-
function(f,angle,col1=1,col2=2)  {
   #hand rotate two factors from a loading matrix
   #see the GPArotation package for much more elegant procedures
     nvar<- dim(f)[2]
     if(!is.matrix(f)) {if(!is.data.frame(f)) {stop("f must be either a data frame or a matrix")} else {f <- as.matrix(f)} }
     rot<- matrix(rep(0,nvar*nvar),ncol=nvar)
     rot[cbind(1:nvar, 1:nvar)] <- 1
     theta<- 2*pi*angle/360
     rot[col1,col1]<-cos(theta)
     rot[col2,col2]<-cos(theta)
     rot[col1,col2]<- -sin(theta)
     rot[col2,col1]<- sin(theta)
     result <- f %*% rot
     return(result) }