A Linear Programming Approach to Rectangular Cartograms

Abstract. In [26], the first two authors of this paper presented the first algorithms to construct rectangular cartograms. The first step is to determine a representation of all regions by rectangles and the second—most important—step is to get the areas of all rectangles correct. This paper presents a new approach to the second step. It is based on alternatingly solving linear programs on the x-coordinates and the y-coordinates of the sides of the rectangles. Our algorithm gives cartograms with considerably lower error and better visual qualities than previous approaches. It also handles countries that cannot be present in any purely rectangular cartogram and it introduces a new way of controlling incorrect adjacencies of countries. Our implementation computes aesthetically pleasing rectangular and nearly rectangular cartograms, for instance depicting the 152 countries of the World that have population over one million.