Redistricting and Graph Partitioning
====================================

The xx2010.graph, xx2010a.graph, and xx2010.xyz files are generated from
U.S. Census 2010 and Tiger/Line 2010 shapefiles. They are freely available
from census.gov web site.
The xx prefix in the filenames are the U.S. Postal Service acronyms of the
state names, e.g. ny is New York.

The .graph and .xyz files are in the metis/jostle/dimacs10 format.
Please consult their website and manuals.

xx2010.graph files (main directory)
------------------
* the vertices are the Census Blocks;
* two vertices have an edge if and only if the corresponding Census Blocks
  share a line segment on their border, i.e. rook-style neighboring.
* vertices are weighted by Census2010 POP100 variable, i.e. the total number
  of persons living in that Census Block.
If you need to map the vertex ID to the Census Block ID, please let me know.

xx2010a.graph files (directory weighted)
-------------------
These are the addon graphs. The vertices and edges are the same, but the
vertex weight is the Land Area of the Census Blocks in square meters, and
the edge weights are the pseudo-length of the shared borderlines.
The pseudo-length is calculated using sqrt(x^2 + y^2), x and y being the
differences in longitudes and latitudes of each line segment on the shared
borderlines, i.e., I didn't use geodesic distances.
[If you need the geodesic distance, please let me know.]
Then the result is multiplied by 10^7 because the metis/jostle file format
wants the edge weights to be integers, and the Census longitudes and latitudes
have 7 decimal places (or maybe 6?).

xx2010.xyz files (directory xyz)
----------------
These are the vertex coordinate files. The vertices are the same, each vertex
(Census Block) gets identified by a point, and the .xyz file gives the
longitudes and latitudes of that point. The points are selected by Census to
be internal to the Census Blocks, but the tech doc says that they are not
always internal (but always very close).

The program to generate the files are at:
http://beorn.googlecode.com


How-to Download
===============
If the obvious options fail (due to large size etc.), you may try:
wget -i xx2010a.graph.urls
wget -i xx2010.graph.urls
wget -i xx2010.xyz.urls.

The three *.urls files are in the archive, you should be able to download
them by clicking in your web-browser. They are just lists of urls.
The wget is a free download program ...


Questions?
Email: milk2cups@gmail.com