Hovertemplate

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

Section

hovertemplate gives full control over the hover label content. Use %{x}, %{y}, %{text}, and D3 format strings like %{y:.2f}. End with <extra></extra> to suppress the default secondary box showing the trace name.

alias Plotly.{Figure, Scatter}

Figure.new()
|> Figure.add_trace(
  Scatter.new(
    x: ["Jan", "Feb", "Mar", "Apr"],
    y: [1200, 950, 1400, 1100],
    mode: "lines+markers",
    hovertemplate: "Month: %{x}<br>Revenue: $%{y:,.0f}<extra></extra>",
    name: "Revenue"
  )
)
|> Figure.update_layout(title: "Custom Hovertemplate")
|> Plotly.show()

Use %{text} to reference an extra text array:

Figure.new()
|> Figure.add_trace(
  Scatter.new(
    x: [1, 2, 3],
    y: [4, 5, 6],
    mode: "markers",
    text: ["Point A", "Point B", "Point C"],
    hovertemplate: "%{text}<br>(%{x}, %{y})<extra></extra>",
    marker: %{size: 12}
  )
)
|> Figure.update_layout(title: "Hovertemplate with Extra Text")
|> Plotly.show()