World Choropleth Map (Robinson Projection)

Mix.install([
  {:plotly_ex, "~> 0.3"},
  {:kino, "~> 0.18"}
])

Section

Choropleth fills countries with colors based on a numeric z: value. locations: must be ISO-3 country codes (3-letter, e.g. "USA", "GBR"). locationmode: "ISO-3" tells Plotly how to match codes to the built-in GeoJSON. geo.projection.type: "robinson" is commonly used for world maps.

alias Plotly.{Figure, Choropleth}

# World happiness index sample data (illustrative)
data = [
  {"FIN", 7.8}, {"DNK", 7.7}, {"CHE", 7.6}, {"ISL", 7.6}, {"NLD", 7.5},
  {"NOR", 7.5}, {"SWE", 7.4}, {"LUX", 7.4}, {"NZL", 7.3}, {"AUT", 7.3},
  {"AUS", 7.2}, {"CAN", 7.2}, {"GBR", 7.1}, {"DEU", 7.0}, {"USA", 6.9},
  {"FRA", 6.7}, {"JPN", 6.1}, {"CHN", 5.6}, {"BRA", 6.3}, {"MEX", 6.5},
  {"RUS", 5.5}, {"IND", 3.8}, {"ZAF", 4.9}, {"EGY", 4.2}, {"ETH", 4.2}
]

locations = Enum.map(data, &elem(&1, 0))
z = Enum.map(data, &elem(&1, 1))
text = Enum.map(data, fn {c, v} -> "#{c}: #{v}" end)

Figure.new()
|> Figure.add_trace(
  Choropleth.new(
    locations: locations,
    z: z,
    text: text,
    locationmode: "ISO-3",
    colorscale: "Viridis",
    colorbar: %{title: %{text: "Happiness"}},
    zmin: 3,
    zmax: 8
  )
)
|> Figure.update_layout(
  title: "World Happiness Index (Illustrative)",
  geo: %{
    projection: %{type: "robinson"},
    showframe: false,
    showcoastlines: true
  }
)
|> Plotly.show()