Fill voronoi polygons with ggplot
<p>i want to fill voronoi polygons with colours based on a variable (z in my case). Here's the code:</p>

<pre><code>library(rgdal)
library(deldir)
library(dplyr)
library(ggplot2)
library(UScensus2010)

x&lt;-c(0,55,105,165,270,65,130,155,155,225,250,295,
     30,100,110,135,160,190,230,300,30,70,105,170,
     210,245,300,0,85,175,300,15,60,90,90,140,210,
     260,270,295,5,55,55,90,100,140,190,255,285,270)
y&lt;-c(305,310,305,310,310,260,255,265,285,280,250,
     260,210,240,225,225,225,230,210,215,160,190,
     190,175,160,160,170,120,135,115,110,85,90,90,
     55,55,90,85,50,50,25,30,5,35,15,0,40,20,5,150)
z&lt;-c(870,793,755,690,800,800,730,728,710,780,804,
     855,813,762,765,740,765,760,790,820,855,812,
     773,812,827,805,840,890,820,873,875,873,865,
     841,862,908,855,850,882,910,940,915,890,880,
     870,880,960,890,860,830)
dati&lt;-data.frame(x,y,z)

vor_pts &lt;- SpatialPointsDataFrame(cbind(dati$x,dati$y),dati, match.ID=TRUE)

SPointsDF_to_voronoi_SPolysDF &lt;- function(sp) {

  # tile.list extracts the polygon data from the deldir computation
  vor_desc &lt;- tile.list(deldir(sp@coords[,1], sp@coords[,2]))

  lapply(1:(length(vor_desc)), function(i) {

    # tile.list gets us the points for the polygons but we
    # still have to close them, hence the need for the rbind
    tmp &lt;- cbind(vor_desc[[i]]$x, vor_desc[[i]]$y)
    tmp &lt;- rbind(tmp, tmp[1,])

    # now we can make the Polygon(s)
    Polygons(list(Polygon(tmp)), ID=i)

  }) -&gt; vor_polygons

  # hopefully the caller passed in good metadata!
  sp_dat &lt;- sp@data

  # this way the IDs _should_ match up w/the data &amp; voronoi polys
  rownames(sp_dat) &lt;- sapply(slot(SpatialPolygons(vor_polygons),
                                  'polygons'),
                             slot, 'ID')

  SpatialPolygonsDataFrame(SpatialPolygons(vor_polygons),
                           data=sp_dat)

}

vor &lt;- SPointsDF_to_voronoi_SPolysDF(vor_pts)

vor_df &lt;- fortify(vor)


ggplot() +
geom_point(data = dati, aes(x, y), shape=21,
           color = "white", fill = "steel blue") +
geom_map(data = vor_df, map = vor_df, aes(x = long, y = lat, map_id = id),
         color = "#a5a5a5", fill = "#FFFFFF00", size = 0.25)
</code></pre>

<p>Now I have this image:</p>

<p><a href="https://i.stack.imgur.com/TzlpD.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/TzlpD.jpg" alt="enter image description here"></a></p>

<p>I want that each polygon should be mapped to a color scale based on the value of variable z... how can i do that?? Thanks!!!</p>