ggplot2 - Drawing colored US State map with cut_number() in R -

i have dataframe called "drawdata":

geoname ranking 1   alabama 15 2   alaska  2 3   arizona 28 4   arkansas    12 5   california  19 6   colorado    7 7   connecticut 42 8   delaware    37 9   district of columbia    9 10  florida 38 11  georgia 11 12  hawaii  48 13  idaho   10 14  illinois    16 15  indiana 26 16  iowa    34 17  kansas  27 18  kentucky    20 19  louisiana   4 20  maine   51 21  maryland    30 22  massachusetts   39 23  michigan    14 24  minnesota   23 25  mississippi 41 26  missouri    32 27  montana 25 28  nebraska    21 29  nevada  45 30  new hampshire   47 31  new jersey  33 32  new mexico  5 33  new york    44 34  north carolina  13 35  north dakota    31 36  ohio    35 37  oklahoma    6 38  oregon  18 39  pennsylvania    40 40  rhode island    49 41  south carolina  29 42  south dakota    46 43  tennessee   43 44  texas   3 45  utah    17 46  vermont 50 47  virginia    8 48  washington  24 49  west virginia   22 50  wisconsin   36 51  wyoming 1 

and want draw state map different colors each ranking. code have is:

  names(drawdata) = c('region','value')   drawdata[,1] = tolower(drawdata[,1])   states = data.frame(state.center, state.abb)   states_map = map_data("state")   df = merge(drawdata, states_map, = "region")   df$num = 49   p1 = ggplot(data = df, aes(x = long, y = lat, group = group))   p1 = p1 + geom_polygon(aes(fill = cut_number(value, num[1])))   p1 = p1 + geom_path(colour = 'gray', linestyle = 2)   p1 = p1 + scale_fill_brewer('', palette = 'purd')   p1 = p1 + coord_map()   p1 = p1 + scale_x_continuous(breaks=null) + scale_y_continuous(breaks=null)   p1 = p1 + theme(legend.position="none")   p1 = p1 + geom_text(data = states, aes(x = x, y = y, label = state.abb, group = null), size = 2)   p1 

this works if 'num', or number of colors fill, small. however, when set 'num=49', produces error:

error in cut.default(x, breaks(x, "n", n), include.lowest = true, ...) :    'breaks' not unique 

when alter code from

p1 = p1 + geom_polygon(aes(fill = cut_number(value, num[1]))) 

to

p1 = p1 + geom_polygon(aes(fill = cut_number(unique(value), num[1]))) 

then gives me different error:

error: aesthetics must either length one, or same length dataproblems:cut_number(unique(value), num[1]) 

i want map every 49 states in map have different colors, each reflecting 'ranking'. appreciated!

brewer palettes deliberately have small maximums (generally < 12) since it's pretty impossible humans map subtle differences discrete values have. can achieve you're looking "faking" scale_fill_gradient2 (note: deliberately left legend in should too):

library(ggplot2)  names(drawdata) <- c('region','value') drawdata[,1] <-  tolower(drawdata[,1])  states <- data.frame(state.center, state.abb) states <- states[!(states$state.abb %in% c("ak", "hi")),] # aren't part of states_map  states_map <- map_data("state")  p1 <- ggplot() # borders p1 <- p1 + geom_map(data=states_map, map=states_map,                     aes(x=long, y=lat, map_id=region),                     color="white", size=0.15) # fills p1 <- p1 + geom_map(data=drawdata, map=states_map,                     aes(fill=value, map_id=region),                     color="white", size=0.15) # labels p1 <- p1 + geom_text(data=states,                       aes(x=x, y=y, label=state.abb, group=null), size=2) # decent projection p1 <- p1 + coord_map("albers", lat0=39, lat1=45) p1 <- p1 + scale_fill_gradient2(low="#f7f4f9", mid="#df65b0", high="#67001f") # better theme p1 <- p1 + labs(x=null, y=null) p1 <- p1 + theme_bw() p1 <- p1 + theme(panel.grid=element_blank()) p1 <- p1 + theme(panel.border=element_blank()) p1 <- p1 + theme(axis.ticks=element_blank()) p1 <- p1 + theme(axis.text=element_blank()) p1 

you can better result scale_fill_distiller alot under scenes let use color brewer palette continuous data (i'd argue not have continuous data tho):

p1 <- p1 + scale_fill_distiller(palette="purd") 

i'd suggest continuing use cut had , having max of 9 breaks fit color brewer palette you're trying work with. in reality, folks still going need table grok rankings (never assume americans know either state shapes, locations or two-letter abbreviations them), i'd pretty suggest using actual table full names @ least choropleth if not in place of it.

note way you're trying build map deliberately excluded alaska, hawaii , district of columbia. you'll need use real shapefile , cover here them show nicely.