These cartograms were computed using the
diffusion model
of
Gastner
and
Newman.
It takes a grid and desired densities and morphs the grid
accordingly. One should start with an
equal-area
map projection
on the original grid so that densities on the globe
are properly reflected by areas on the deformed
grid.
I used
the
Hobo-Dyer projection.
The cartograms here represent three different types of input data:
coverages
which directly specify a density for coordinates on the globe,
total (proportional) areas for countries, and
scaling for areas of countries. Country-level data
was applied to all parts of the country equally;
thus, for instance, in the cereal production map Alaska is
far larger than it would have been if considered on its own.
Air pollution
Area is scaled by estimated
PM2.5
density.
Coverage from the
Atmospheric Composition Analysis Group
Caloric intake
Countries are scaled by
excess of average kcal/person/day over the
FAO-estimated
minimum of 1800. Data from the
FAOSTAT
Food Balance Sheets
Cereal production
Area of countries is proportional to production of
cereals used for grain. Data from the
FAOSTAT
Food Balance Sheets
IP addresses
Area of countries is proportional to number
of allocated
IPv4
addresses. Data from
MaxMind
Top universities
Area of countries is proportional to number
of top 400 universities according to
U.S. News & World Report.
Data from
World University Rankings
The
diffusion model
was computed using the
cart package.
The country outlines are from the
Natural Earth
database and were parsed with
shapelib.
I
four-colored
the countries using the
FAO's
geopolitical ontology
to determine which countries share a border.
The four colors are from the
pooltime
color scheme and the background ocean color is from
Seashells.
One of the coverages was in
ArcInfo
format, and it was parsed with the
aigrid
library which I extracted from
GDAL.
Country-level data was processed into lists sorted by
ISO 3166-1 alpha-2
country code.
This coding system is not perfect; for instance, some
datasets consider the
Netherlands Antilles
to be a country and some do not. In most cases the problematic
areas were negligible in size.
