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Regarding your questions on my third question, the data for the shapefiles
and database files are taken from National Historical Geographic Information
System (NHGIS), which in addition to providing these also provides census
2000 data. The polygons do, I believe, have vertices, and they are of
varying sizes; this goes for tract polygons as well as county polygons. The
greater the population density the smaller the tracts/counties, the more
sparse the population the bigger the polygons. And, yes, I am trying to
calculate xy coordinates of the centroids to match the xy coordinates of
geocoded addresses of US postsecondary institutions. As I am not too
familiar with the various coordinate systems in use, I can't talk to that
issue. Suffice it to be shown that there is a huge discrepancy between
(-681360.7, 575246.7) and (-86.16864, 32.38251), and I don't know how to
make them equivalent in expression.
I hope this was a bit clearer than my previous post.
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