Filled Scattermap Trace

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

Section

Scattermap with fill: "toself" closes the lat/lon path and fills the enclosed area. fillcolor: with rgba allows transparency so the tile map shows through. Close the polygon by repeating the first point at the end.

alias Plotly.{Figure, Scattermap}

# Approximate boundary of the state of Colorado (rectangular)
lat = [41.0, 41.0, 37.0, 37.0, 41.0]
lon = [-109.05, -102.05, -102.05, -109.05, -109.05]

Figure.new()
|> Figure.add_trace(
  Scattermap.new(
    lat: lat,
    lon: lon,
    mode: "lines",
    fill: "toself",
    fillcolor: "rgba(0, 0, 255, 0.2)",
    line: %{color: "blue", width: 2},
    name: "Colorado"
  )
)
|> Figure.update_layout(
  title: "Filled Scattermap — Colorado Boundary",
  map: %{
    style: "carto-positron",
    center: %{lat: 39.0, lon: -105.5},
    zoom: 5
  }
)
|> Plotly.show()