ggplot map with l

Question

I want to plot a world map using ggplot2 (v.9) which combines two pieces if information. The following example illustrates:

library(rgdal)
library(ggplot2)
         


        

Answer 1

One option is to map growth to the size of some points plotted at the centroid of the polygons.

centroids <- as.data.frame(coordinates(world.map))
df <- data.frame(df,centroids)

choropleth <-ggplot() +
     geom_map(aes(fill = category, map_id = id),data = df, map =world.ggmap) +
     expand_limits(x = world.ggmap$long, y = world.ggmap$lat) + 
    scale_fill_hue(na.value=NA)
choropleth



choropleth + geom_point(aes(x=V1,y=V2,size=growth),data=df) +
    scale_area(range=c(0,3))

Or if you really want to double code color, you could color the points instead. Note, that you can also add a raster map of satellite imagery with the new OpenStreetMap package (shameless plug).

library(OpenStreetMap)
library(raster)
rastermap <- openmap(c(70,-179),
        c(-70,179),zoom=2,type='bing')
rastermap <- openproj(rastermap)
autoplot(rastermap,expand=FALSE) +
     geom_map(aes(x=70,y=70,fill = category, map_id = id),data = df,
        map =world.ggmap) +
     expand_limits(x = world.ggmap$long, y = world.ggmap$lat) + 
    scale_fill_hue(na.value=NA) + 
    geom_point(aes(x=V1,y=V2,colour=growth),data=df) +
    scale_colour_gradient(low = "red", high = "blue", 
        guide = "colorbar",na.value=NA)

Answer 2

I would use different hue ranges for fill and line color:

ggplot(df, aes(map_id = id)) +
  geom_map(aes(fill = growth, color = category), map =world.ggmap) +
  expand_limits(x = world.ggmap$long, y = world.ggmap$lat) +
  scale_fill_gradient(high = "red", low = "white", guide = "colorbar") +
  scale_colour_hue(h = c(120, 240))

OR, use fill for category and transparency for growth level.

ggplot(df, aes(map_id = id)) +
  geom_map(aes(alpha = growth, fill = category), map =world.ggmap) +
  expand_limits(x = world.ggmap$long, y = world.ggmap$lat) +
  scale_alpha(range = c(0.2, 1), na.value = 1)

It depends on what you want to show.

Just in case, here is the way to change the linesize:

ggplot(df, aes(map_id = id)) +
 geom_map(aes(fill = growth, color = category, size = factor(1)), map =world.ggmap) +
 expand_limits(x = world.ggmap$long, y = world.ggmap$lat) +
 scale_fill_gradient(high = "red", low = "white", guide = "colorbar") +
 scale_colour_hue(h = c(120, 240)) + 
 scale_size_manual(values = 2, guide = FALSE)

Here is HSV version:

df$hue <- ifelse(is.na(df$category), 0, as.numeric(df$category)/max(as.numeric(df$category), na.rm=T))
df$sat <- ifelse(is.na(df$growth), 0, df$growth/max(df$growth, na.rm=T))
df$fill <- ifelse(is.na(df$category), "grey50", hsv(df$hue, df$sat))

ggplot(df, aes(map_id = id)) +
 geom_map(aes(fill = fill), map =world.ggmap) +
 expand_limits(x = world.ggmap$long, y = world.ggmap$lat) +
 scale_fill_identity(guide = "none")