Voronoi Cartogram with Elastic Boundary¶

Population cartogram of US States where the outer boundary deforms to reduce area errors at the periphery.

Load dataset and run with a fixed boundary (left) and elastic boundary (right).

import matplotlib

matplotlib.use("Agg")
import matplotlib.pyplot as plt

import carto_flow.data as examples
import carto_flow.voronoi_cartogram as vor

us_states = examples.load_us_census(population=True)

opts = vor.VoronoiOptions(n_iter=300, area_cv_tol=0.05)

result_fixed = vor.create_voronoi_cartogram(
    us_states,
    weights="Population (Millions)",
    backend=vor.RasterBackend(resolution=256, boundary=None),
    options=opts,
)

result_elastic = vor.create_voronoi_cartogram(
    us_states,
    weights="Population (Millions)",
    backend=vor.RasterBackend(resolution=256, boundary=vor.ElasticBoundary(strength=0.05)),
    options=opts,
)

Plot the two results side by side.

fig, axes = plt.subplots(1, 2, figsize=(14, 5))
for ax, res, title in zip(
    axes,
    [result_fixed, result_elastic],
    ["Fixed boundary", "ElasticBoundary(strength=0.05)"],
    strict=False,
):
    res.plot(
        "Population (Millions)",
        ax=ax,
        cmap="RdYlGn_r",
        vmin=0,
        vmax=40,
        legend=True,
        legend_kwds={"shrink": 0.6, "label": "Population (Millions)"},
    )
    ax.set(title=title)
    ax.axis("off")
plt.tight_layout()

Fixed boundary, ElasticBoundary(strength=0.05)

Total running time of the script: ( 0 minutes 3.915 seconds)

Download Python source code: plot_voronoi_elastic_boundary.py

Download Jupyter notebook: plot_voronoi_elastic_boundary.ipynb

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