# Map Projections for R Shapefiles: United States

November 2, 2016
By

(This article was first published on R Tricks, and kindly contributed to R-bloggers)

Someone contacted me recently about the map projections used in my blscrapeR package. After a bit of web searching, I couldn’t find a really good list of map projections for the continental U.S. that could be used in R. This list is as much for my own reference as anyone else, but hope you find it useful.

Here’s my list of map projections that are appropriate to map the continental U.S. in R. DISCLAIMER: I have omitted many, if you like another, comment and I’ll add to the list. The full code is below in Gist form. There are many other projections listed here, I just displayed the ones I find most useful.

The Native Map Projection
U-g-l-y, you ain’t got no alibi!

```# Default projection of the map can be found by running the following on the SpatialPolyGonsDataFrame.
raster::crs(county)

# Then apply the result to the CRS() functions.
us.map <- spTransform(state, CRS("+proj=longlat +datum=NAD83 +no_defs +ellps=GRS80 +towgs84=0,0,0"))
```

Mercator Projection

```# Mercator projection.
us.map <- spTransform(state, CRS("+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0
+x_0=0.0 +y_0=0 +k=1.0 +units=m +no_defs"))
```

Lambert Azimuthal Equal Area Projection

```# Lambert Azimuthal Equal Area
us.mpa <- spTransform(state, CRS("+proj=laea +lat_0=52 +lon_0=10 +x_0=4321000 +y_0=3210000
+ellps=GRS80 +units=m +no_defs"))
```

Lambert Conformal Conic Projection

```# Lambert Conformal Conic
us.mpa <- spTransform(state, CRS("+proj=lcc +lat_1=33 +lat_2=45 +lat_0=39 +lon_0=-96
```

Albers Equal Area Projection

```# Albers Equal Area
us.mpa <- spTransform(state, CRS("+proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0
```

Albers Equal Area Conic Projection

```# Albers Equal Area Conic
us.mpa <- spTransform(state, CRS("+proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=37.5 +lon_0=-96
```

Full Code
Here's the full script I used, including all of the projection arguments, shapefile and mapping data.

R-bloggers.com offers daily e-mail updates about R news and tutorials on topics such as: Data science, Big Data, R jobs, visualization (ggplot2, Boxplots, maps, animation), programming (RStudio, Sweave, LaTeX, SQL, Eclipse, git, hadoop, Web Scraping) statistics (regression, PCA, time series, trading) and more...