more readme

README.md

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 # reag
 Reaggregation process for translating historical data to current boundaries.
+
+== Installation
+
+Reag uses Python 2.6+, pyshp, and shapely.
+
+Follow the instructions on https://github.com/GeospatialPython/pyshp and http://toblerity.org/shapely/project.html#installation to install these dependencies.
+
+== Use
+
+```
+python getvalues.py <historical-shapefile> <values-csv> <values-column> <type>
+```
+
+The historical shapefile and values csv must represent the same year.
+type may be SUM or AVG.
+
+For example,
+```
+python getvalues.py nhgis0005_shapefile_tl2000_us_county_1950/US_county_1950 nhgis0001_ts_1950_county.csv A00AA1950 sum
+```