assignColors.R

assignColors.R

# this function takes an input numeric vector and 
# partitions it into a set number of breaks
# it then assigns a color to each break via RColorBrewer

assignColors <- function(var, 
                         n = 9, # number of colors / breaks
                         style = "jenks", # can be changed to other methods in "classIntervals"
                         pal = "RdYlBu", # Palettes from RColorBrewer
                         na_color ='#787878', # Color to give NA's
                         na_omit = FALSE, # Logical, argument above will be irrelevant if TRUE
                         alph=0.5 # Opacity (0-1)
                         ) {

    # load required libraries
    require("classInt")
    require("scales")
    require("RColorBrewer")
    require("plyr")

    # na_omit?
    if (na_omit) {
      var <- var[!is.na(var)]
    }

    # create colors 
    cols <- brewer.pal(n, pal)

    # create breaks
    cuts <- classIntervals(var, n, style=style)
    breaks <- cut(var, breaks=cuts$brks, labels=FALSE)
    
    # create function
    assignColor <- function(x) {
                     if(is.na(x)) {
                        assignment <- alpha(na_color, alph)
                     } else {
                        assignment <- alpha(cols[x], alph)
                     }
                   return(assignment)
                }

    # assign colors to breaks
    assignments <- unlist(llply(breaks, assignColor, .progress="text"))
    return(assignments)
}