This page contains computer software and documentation for creating
density-equalizing maps or "cartograms" using the technique described in
the paper Diffusion-based
method for producing density equalizing maps, Michael T. Gastner and
M. E. J. Newman, Proc. Natl. Acad. Sci. USA101, 7499-7504
For documentation on how to use the software, click here.
To see some examples of cartograms created
using this software take a look at my cartograms web
page or the recent book The
Atlas of the Real World, a collaborative project of myself and
co-authors Daniel Dorling and Anna Barford.
Questions or comments
I welcome questions about the code, suggestions for improvement, or any
other comments. My contact details are here.
Other cartogram software
My collaborator Michael Gastner has also written a program to calculate
cartograms using our diffusion-based method. You can find his code here. There are several
technical differences between Dr. Gastner's code and mine, including the
implementation of the Fourier transforms, the integrator used to solve the
flow equations, and the method used to evaluate the velocity field. In
practice, this means that the code given here runs somewhat faster than
Dr. Gastner's code (typically about a factor of six or seven faster). The
two programs are entirely independent, sharing no code whatsoever, which
allows you to make an independent check of the results, should you wish to
do so. (I know of no case in which the programs disagree.)
A user-friendly JAVA program implementing our cartogram method called
ScapeToad has been developed by programmers at the Choros Laboratory in
Lausanne. You can find it here. There is
also an (unrelated) on-line JAVA version of our method created by Frank
Hardisty, which you can find here, and
there are free cartogram add-ons for ArcGIS and MapInfo. There is an R
version of the code given here called RCartogram, which you can find here.
The original algorithm upon which this software is based was developed in
collaboration with Michael
Gastner. I received useful feedback from Tom Gross and Danny Dorling
during the development of the software. I'd also like to acknowledge the
Santa Fe Institute for hospitality
while some of the development work was completed.