Mapping and reducing

with-descartes-reduce.py

# Making maps with reduce()

from matplotlib import pyplot
from descartes import PolygonPatch
from fiona import collection

BLUE = '#6699cc'

def render(axes, rec):
    """Given matplotlib axes and a record, adds the record as a patch
    and returns the axes so that reduce() can accumulate more
    patches."""
    axes.add_patch(
        PolygonPatch(rec['geometry'], fc=BLUE, ec=BLUE, alpha=0.5, zorder=2))
    return axes

# Set up the figure and axes.
figure = pyplot.figure(1, figsize=(6, 6), dpi=90)
axes = figure.add_subplot(111)

# Open a file and render every feature into the plot axes.
with collection("docs/data/test_uk.shp", "r") as source:
    reduce(render, source, axes)

axes.autoscale(tight=True)
# We could also set limits explicitly:
# minx, miny, maxx, maxy = source.bounds
# axes.set_xlim(minx, maxx)
# axes.set_ylim(miny, maxy)
figure.savefig('with-descartes-functional.png')