# linearly transforms a numeric object to fit a different range.
# could use a few more sanity checks

rescale<-function(x,newrange) {
 if(nargs() > 1 && is.numeric(x) && is.numeric(newrange)) {
  # if newrange has max first, reverse it
  if(newrange[1] > newrange[2]) {
   newmin<-newrange[2]
   newrange[2]<-newrange[1]
   newrange[1]<-newmin
  }
  xrange<-range(x)
  if(xrange[1] == xrange[2]) stop("can't rescale a constant vector!")
  mfac<-(newrange[2]-newrange[1])/(xrange[2]-xrange[1])
  invisible(newrange[1]+(x-xrange[1])*mfac)
 }
 else {
  cat("Usage: rescale(x,newrange)\n")
  cat("\twhere x is a numeric object and newrange is the min and max of the new range\n")
 }
}