Created
January 9, 2015 01:56
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Census data to zipcode center.
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import itertools as IT | |
def area_of_polygon(x, y): | |
"""Calculates the signed area of an arbitrary polygon given its verticies | |
http://stackoverflow.com/a/4682656/190597 (Joe Kington) | |
http://softsurfer.com/Archive/algorithm_0101/algorithm_0101.htm#2D%20Polygons | |
""" | |
area = 0.0 | |
for i in range(-1, len(x) - 1): | |
area += x[i] * (y[i + 1] - y[i - 1]) | |
return area / 2.0 | |
def centroid_of_polygon(points): | |
""" | |
http://stackoverflow.com/a/14115494/190597 (mgamba) | |
""" | |
area = area_of_polygon(*zip(*points)) | |
result_x = 0 | |
result_y = 0 | |
N = len(points) | |
points = IT.cycle(points) | |
x1, y1 = next(points) | |
for i in range(N): | |
x0, y0 = x1, y1 | |
x1, y1 = next(points) | |
cross = (x0 * y1) - (x1 * y0) | |
result_x += (x0 + x1) * cross | |
result_y += (y0 + y1) * cross | |
result_x /= (area * 6.0) | |
result_y /= (area * 6.0) | |
return (result_x, result_y) | |
import shapefile | |
sf = shapefile.Reader("cb_2013_us_zcta510_500k.shp") | |
shapes = sf.iterShapes() | |
records = sf.iterRecords() | |
for sh, rec in zip(shapes, records): | |
print("zipcode: %s" % rec[0]) | |
print(centroid_of_polygon(sh.points)) |
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