r - 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)
library(maptools)

# Data from http://thematicmapping.org/downloads/world_borders.php.
# Direct link: http://thematicmapping.org/downloads/TM_WORLD_BORDERS_SIMPL-0.3.zip
# Unpack and put the files in a dir 'data'

gpclibPermit()
world.map <- readOGR(dsn="data", layer="TM_WORLD_BORDERS_SIMPL-0.3")
world.ggmap <- fortify(world.map, region = "NAME")

n <- length(unique(world.ggmap$id))
df <- data.frame(id = unique(world.ggmap$id),
                 growth = 4*runif(n),
                 category = factor(sample(1:5, n, replace=T)))

## noise
df[c(sample(1:100,40)),c("growth", "category")] <- NA


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(low = "red", high = "blue", guide = "colorbar")

However, this solution is not a nice way to display both growth and category. Growth is highly visible, but category is almost impossible to see because it is just a border.

I have tried to increase the size of borders, but without luck (the new geom_map is hard to work with). Does anyone knows how to increase border size in the above example, or even better, a mechanism to display two factors?

A bonus question: country names, such as those used by the maps package (which features USSR!) are the data used in the example is fragile. I prefer to use ISO 3166-1 alpha-3(1). Does anyone know data readily usable with ggplot2 which features ISO-... country names (included in linked data)

Result:

result http://ompldr.org/vY3hsYQ

Answer 1

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")