Trace Opacity

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

Section

The opacity property on a trace applies to the entire trace — markers, lines, and fill all become equally transparent. This is different from marker.opacity which only affects the marker symbols.

Use trace opacity when you want overlapping traces to show through each other while keeping a consistent visual weight for each trace.

alias Plotly.{Figure, Scatter}

xs = Enum.to_list(0..20)

Figure.new()
|> Figure.add_trace(Scatter.new(
  x: xs,
  y: Enum.map(xs, fn x -> :math.sin(x / 3.0) * 4 + 5 end),
  mode: "lines+markers",
  fill: "tozeroy",
  name: "opacity: 0.6",
  opacity: 0.6,
  marker: %{size: 8}
))
|> Figure.add_trace(Scatter.new(
  x: xs,
  y: Enum.map(xs, fn x -> :math.cos(x / 3.0) * 4 + 5 end),
  mode: "lines+markers",
  fill: "tozeroy",
  name: "opacity: 0.6",
  opacity: 0.6,
  marker: %{size: 8}
))
|> Figure.update_layout(title: "Trace Opacity — affects markers, line, and fill equally")
|> Plotly.show()