Relocating Alaska and Hawaii on thematic map of the USA with ggplot2

Question

I am trying to create a thematic map showing all 50 US states, but I am having trouble relocating Alaska and Hawaii in a reliable way. I have a couple of ideas but none of them work well. I will demonstrate them now. First we need to import the data; using the data in the `maps` package is not enough because it does not include Hawaii and Alaska. ``` setwd(tempdir()) download.file("https://dl.dropbox.com/s/wl0z5rpygtowqbf/states_21basic.zip?dl=1", "usmapdata.zip", method = "curl") # This is a mirror of http://www.arcgis.com/home/item.html? # id=f7f805eb65eb4ab787a0a3e1116ca7e5 unzip("usmapdata.zip") require(rgdal) all_states <- readOGR("states_21basic/", "states") require(ggplot2); require(maptools); require(rgeos); require(mapproj); all_states <- fortify(all_states, region = "STATE_NAME") ``` Now we define some plot aesthetics: ``` p <- ggplot() + geom_polygon( aes(x=long, y=lat, group = group, fill = as.numeric(as.factor(id))), colour="white", size = 0.25 ) + coord_map(projection="a…

Accepted Answer

Here's how to do it by projecting and transforming. You will need:

```
require(maptools)
require(rgdal)

fixup <- function(usa,alaskaFix,hawaiiFix){

alaska=usa[usa$STATE_NAME=="Alaska",]
  alaska = fix1(alaska,alaskaFix)
  proj4string(alaska) <- proj4string(usa)

hawaii = usa[usa$STATE_NAME=="Hawaii",]
  hawaii = fix1(hawaii,hawaiiFix)
  proj4string(hawaii) <- proj4string(usa)

usa = usa[! usa$STATE_NAME %in% c("Alaska","Hawaii"),]
  usa = rbind(usa,alaska,hawaii)

return(usa)

}

fix1 <- function(object,params){
  r=params[1];scale=params[2];shift=params[3:4]
  object = elide(object,rotate=r)
  size = max(apply(bbox(object),1,diff))/scale
  object = elide(object,scale=size)
  object = elide(object,shift=shift)
  object
}
```

Then read in your shapefile. Use `rgdal`:

```
us = readOGR(dsn = "states_21basic",layer="states")
```

Now transform to equal-area, and run the fixup function:

```
usAEA = spTransform(us,CRS("+init=epsg:2163"))
usfix = fixup(usAEA,c(-35,1.5,-2800000,-2600000),c(-35,1,6800000,-1600000))
plot(usfix)
```

The parameters are rotations, scaling, x and y shift for Alaska and Hawaii respectively, and were obtained by trial and error. Tweak them carefully. Even changing Hawaii's scale parameter to 0.99999 sent it off the planet because of the large numbers involved.

If you want to turn this back to lat-long:

```
usfixLL = spTransform(usfix,CRS("+init=epsg:4326"))
plot(usfixLL)
```

But I'm not sure if you need to use the transformations in `ggplot` since we've done that with `spTransform`.

You can now jump through the `ggplot2` fortify business. I'm not sure if it matters for you but note that the order of the states is different in the `usfix` version - Alaska and Hawaii are now the last two states.

Relocating Alaska and Hawaii on thematic map of the USA with ggplot2

Solution

Problem