Create Cartograms with R

Construct continuous and non-contiguous area cartograms.

cartogram: Create Cartograms with R

Construct a continuous area cartogram by a rubber sheet distortion algorithm (Dougenik et al. 1985), non-contiguous Area Cartograms (Olson 1976), and non-overlapping Circles Cartogram (Dorling el al. 1996) in R.

Installation

You can install the cartogram package from CRAN as follows:

install.packages("cartogram")

To upgrade to the latest development version of cartogram, install the package devtools and run the following command:

devtools::install_github("sjewo/cartogram")

NEWS

• [0.3.0] Remove sp, rgdal and maptools from examples and suggestions. cartogram_cont has a new parameter verbose = FALSE to hide print of size error on each iteration.
• [0.2.0] Migrated all functions to sf, fixed problems with multipolygons. cartogram functions won’t accept features with longitude/latitude coordinates anymore.
• [0.1.1] Update sf code: Thanks to @Nowosad for speeding things up!
• [0.1.0] Non-Overlapping Circles Cartogram (Dorling)
• [0.0.3] sf support added
• [0.0.2] Non-contiguous Area Cartogram
• [0.0.2] Prepare data with missing or extreme values before cartogram calculation for faster convergence
• [0.0.1] Initial Release

Examples

Continuous Area Cartogram

library(cartogram)
library(sf)
#> Linking to GEOS 3.11.0, GDAL 3.5.3, PROJ 9.1.0; sf_use_s2() is TRUE
library(tmap)

data("World")

# keep only the african continent
afr <- World[World$continent == "Africa", ]

# project the map
afr <- st_transform(afr, 3395)

# construct cartogram
afr_cont <- cartogram_cont(afr, "pop_est", itermax = 5)

# plot it
tm_shape(afr_cont) + tm_polygons("pop_est", style = "jenks") +
  tm_layout(frame = FALSE, legend.position = c("left", "bottom"))

Non-contiguous Area Cartogram

Many thanks to @rCarto and @neocarto for contributing the code!

# construct cartogram
afr_ncont <- cartogram_ncont(afr, "pop_est")

# plot it
tm_shape(afr) + tm_borders() +
  tm_shape(afr_ncont) + tm_polygons("pop_est", style = "jenks") +
  tm_layout(frame = FALSE, legend.position = c("left", "bottom"))

Non-Overlapping Circles Cartogram

Many thanks to @rCarto for contributing the code!

# construct cartogram
afr_dorling <- cartogram_dorling(afr, "pop_est")

# plot it
tm_shape(afr) + tm_borders() +
  tm_shape(afr_dorling) + tm_polygons("pop_est", style = "jenks") +
  tm_layout(frame = FALSE, legend.position = c("left", "bottom"))

References

• Dorling, D. (1996). Area Cartograms: Their Use and Creation. In Concepts and Techniques in Modern Geography (CATMOG), 59.
• Dougenik, J. A., Chrisman, N. R., & Niemeyer, D. R. (1985). An Algorithm To Construct Continuous Area Cartograms. In The Professional Geographer, 37(1), 75-81.
• Olson, J. M. (1976), Noncontiguous Area Cartograms. The Professional Geographer, 28: 371–380. doi:10.1111/j.0033-0124.1976.00371.x