def three_by_three_grid():
"""Returns a graph that looks like this:
0 1 2
3 4 5
6 7 8
"""
graph = Graph()
graph.add_edges_from([
(0, 1),
(0, 3),
(1, 2),
(1, 4),
(2, 5),
(3, 4),
(3, 6),
(4, 5),
(4, 7),
(5, 8),
(6, 7),
(7, 8),
])
return graph
from gerrychain import Partition, Graph
import math
from gerrychain.metrics.compactness import compute_polsby_popper, polsby_popper
from gerrychain.updaters import (
Tally,
boundary_nodes,
cut_edges,
cut_edges_by_part,
exterior_boundaries,
interior_boundaries,
perimeter,
)
from gerrychain.partition.geographic import GeographicPartition
graph = Graph()
graph.add_edges_from([(0, 1), (1, 2), (2, 0)])
AREA_COL = 'area'
PERIM_COL = 'perimeter'
graph.nodes[0][AREA_COL] = 40
graph.nodes[0][PERIM_COL] = 18
graph.nodes[0][AREA_COL] = 120
graph.nodes[0][PERIM_COL] = 120
graph.nodes[0][AREA_COL] = 30
graph.nodes[0][PERIM_COL] = 20
partition = GeographicPartition(graph, {
0: 0,
from gerrychain import Partition, Graph
import math
from gerrychain.metrics.compactness import compute_polsby_popper, polsby_popper
graph = Graph()
graph.add_edges_from([(0, 1), (1, 2), (2, 0)]) # Arbitrary. copied this from Updaters documentation
POP_COL = 'vap'
VRA_POP_COL = 'bvap'
AREA_COL = 'area'
PERIM_COL = 'perimeter'
'''
Fake data here. Node 0 and 2 have enough to qualify alone, but pairing/districting
Node 1 with either can tank it.
'''
graph.nodes[0][POP_COL] = 100
graph.nodes[0][VRA_POP_COL] = 60
graph.nodes[1][POP_COL] = 100
graph.nodes[1][VRA_POP_COL] = 0
graph.nodes[2][POP_COL] = 100
graph.nodes[2][VRA_POP_COL] = 40
def num_vra_districts(partition, pop_col=POP_COL, vra_pop_col=VRA_POP_COL, vra_relative_threshold=0.37):
# we'll count districts that satisfy the VRA threshold.
total = 0
# For each district,...
