# fields, Tools for spatial data
# Copyright 2004-2007, Institute for Mathematics Applied Geosciences
# University Corporation for Atmospheric Research
# Licensed under the GPL -- www.gpl.org/licenses/gpl.html

"fast.1way" <-
function (lev, y, w = rep(1, length(y))) 
{
# w are proportional to reciprocal variance.
  
    if( !is.matrix(y)){
      y<- as.matrix(y)}
    
    N <- nrow(y)
    NC<- ncol(y)
# ordered unique values of lev
    tags <- lev[!duplicated(lev)]
    NR<- length( tags)
                
# lev are now integer tags
    lev <- match(lev, tags)

#
        means<- matrix( NA, nrow=NR,ncol=NC)
# add together weights with same lev
        w.means<- c(tapply( w, lev, sum))

    for( k in 1:NC){    
# find weighted means for each lev
       means[,k] <- (tapply( y[,k]*w, lev, sum)/w.means)}
    
# find SS
    SSE <- colSums((w * (y - means[lev,])^2))
    MSE <- SSE/(N - NR)

  list(n=N , means = means, SSE = SSE, w.means = w.means, 
        MSE = MSE, lev = lev, tags=tags)
}