Standardize value ranks between [0, 1]

rank_stand.R

# Based on:
# http://stackoverflow.com/questions/4401498/how-to-rank-values-in-a-vector-and-give-them-corresponding-values
# http://stackoverflow.com/questions/5468280/scale-a-series-between-two-points-in-r/5468527#5468527

values <- runif(1000000)

# replace runif with getValues(raster)
ranks <- as.numeric(factor(values))

# Transform variables to a scale between 0 and 1, while retaining rank order and 
# the relative size of separation between values. 

range01 <- function(x) {
  return((x-min(x)) / (max(x) - min(x)))
}

stand.ranks <- range01(ranks)

# Check the difference between elements in stand.ranks
diff(sort(stand.ranks))