Polar Chart Directions

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

Section

By default, theta: 0 is at the right (3 o'clock) and increases counter-clockwise. layout.polar.angularaxis.direction: "clockwise" reverses the rotation direction. layout.polar.angularaxis.rotation: N sets where theta: 0 is (in degrees from right). Setting rotation: 90 moves 0° to the top (12 o'clock), which is conventional for compass bearings.

alias Plotly.{Figure, Scatterpolar}

theta = Enum.map(0..11, fn i -> i * 30 end)
r     = [3, 2, 4, 3, 2, 5, 4, 3, 2, 4, 3, 2]

Figure.new()
|> Figure.add_trace(
  Scatterpolar.new(
    r: r ++ [hd(r)],
    theta: theta ++ [hd(theta)],
    mode: "lines+markers",
    fill: "toself",
    name: "Counter-clockwise (default)"
  )
)
|> Figure.update_layout(
  title: "Default direction (counter-clockwise, 0° at right)"
)
|> Plotly.show()

Figure.new()
|> Figure.add_trace(
  Scatterpolar.new(
    r: r ++ [hd(r)],
    theta: theta ++ [hd(theta)],
    mode: "lines+markers",
    fill: "toself",
    name: "Clockwise, 0° at top"
  )
)
|> Figure.update_layout(
  title: "Clockwise direction, 0° at top (compass convention)",
  polar: %{
    angularaxis: %{
      direction: "clockwise",
      rotation: 90
    }
  }
)
|> Plotly.show()