R/insert.mds.generic.R

In dill/msg: Multidimensional Scaling for Generalized Additive Models

# generic MDS insertion routine
# will call the WAD version if bnd is supplied
insert.mds.generic <- function(mds.obj, new.points, old.points, dist_fn,
                               bnd=NULL){

  # if bnd supplied return what insert.mds() returns
  if(!is.null(bnd)){
    return(insert.mds(new.points, old.points,mds.obj,bnd))
  }

  # otherwise do the non-WAD thing...
  big.points <- rbind(old.points,new.points)
  ind <- 1:nrow(old.points)
  ind2 <- (nrow(old.points)+1):nrow(big.points)

  rm(old.points, new.points)
  gc()

  lambda.inverse <- diag(1/mds.obj$eig[1:dim(mds.obj$points)[2]])

  new.dist <- as.matrix(dist_fn(big.points))[ind,, drop=FALSE]

  new.dist <- new.dist[,ind2]
  S <- -1/2*mds.obj$x
  d <- -(new.dist^2-diag(S))
  mds.points <- t(1/2*(lambda.inverse %*% t(mds.obj$points) %*% d))

  return(mds.points)
}