Grouped Legend

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

Section

Assign the same legendgroup string to multiple traces to group them in the legend. Clicking the group entry toggles all traces in the group at once. Use legendgrouptitle: %{text: "..."} to add a title above the group.

alias Plotly.{Figure, Scatter}

Figure.new()
|> Figure.add_trace(
  Scatter.new(
    x: [1, 2, 3], y: [2, 4, 3],
    name: "Line A",
    mode: "lines",
    legendgroup: "group1",
    legendgrouptitle: %{text: "Group 1"}
  )
)
|> Figure.add_trace(
  Scatter.new(
    x: [1, 2, 3], y: [2.2, 3.8, 3.2],
    name: "Line A (variant)",
    mode: "lines",
    line: %{dash: "dot"},
    legendgroup: "group1"
  )
)
|> Figure.add_trace(
  Scatter.new(
    x: [1, 2, 3], y: [4, 2, 5],
    name: "Line B",
    mode: "lines",
    legendgroup: "group2",
    legendgrouptitle: %{text: "Group 2"}
  )
)
|> Figure.add_trace(
  Scatter.new(
    x: [1, 2, 3], y: [3.8, 2.2, 4.8],
    name: "Line B (variant)",
    mode: "lines",
    line: %{dash: "dot"},
    legendgroup: "group2"
  )
)
|> Figure.update_layout(title: "Grouped Legend")
|> Plotly.show()