Add Multiple Traces

Mix.install([
  {:plotly_ex, "~> 0.3"},
  {:kino, "~> 0.18"},
  {:req, "~> 0.5"}
])

Section

This example visualizes flow over a Karman-Trefftz airfoil using multiple traces on a Carpet grid. The dataset is fetched from GitHub. The visualization combines:

• A Carpet base grid defining the coordinate system
• A filled Contourcarpet for pressure coefficient (cp) values
• A Contourcarpet for streamlines (coloring: "none", ncontours: 50)
• A Contourcarpet for pressure contour lines
• Scatter traces for the airfoil surface shape

alias Plotly.{Figure, Carpet, Scattercarpet, Contourcarpet, Scatter}

url = "https://raw.githubusercontent.com/bcdunbar/datasets/master/airfoil_data.json"
json = url |> Req.get!() |> Map.get(:body) |> Jason.decode!()

Figure.new()
|> Figure.add_trace(
  Carpet.new(
    carpet: "c1",
    a: json |> List.first() |> Map.get("a"),
    b: json |> List.first() |> Map.get("b"),
    x: json |> List.first() |> Map.get("x"),
    y: json |> List.first() |> Map.get("y"),
    aaxis: %{
      startlinewidth: 2,
      startline: true,
      showticklabels: "none",
      endline: true,
      showgrid: false,
      endlinewidth: 2,
      smoothing: 0
    },
    baxis: %{
      startline: false,
      endline: false,
      showticklabels: "none",
      smoothing: 0,
      showgrid: false
    }
  )
)
|> Figure.add_trace(
  Contourcarpet.new(
    carpet: "c1",
    name: "Pressure",
    z: json |> Enum.at(1) |> Map.get("z"),
    autocolorscale: false,
    colorscale: "Viridis",
    zmin: -8,
    zmax: 1,
    autocontour: false,
    zauto: false,
    contours: %{start: -1, size: 0.025, end: 1.0, showlines: false},
    line: %{smoothing: 0},
    colorbar: %{
      y: 0,
      yanchor: "bottom",
      len: 0.75,
      title: %{text: "Pressure coefficient, c<sub>p</sub>"}
    }
  )
)
|> Figure.add_trace(
  Contourcarpet.new(
    carpet: "c1",
    name: "Streamlines",
    z: json |> Enum.at(2) |> Map.get("z"),
    opacity: 0.3,
    showlegend: true,
    autocontour: true,
    ncontours: 50,
    contours: %{coloring: "none"},
    line: %{color: "white", width: 1}
  )
)
|> Figure.add_trace(
  Contourcarpet.new(
    carpet: "c1",
    name: "Pressure<br>contours",
    z: json |> Enum.at(3) |> Map.get("z"),
    showlegend: true,
    autocontour: false,
    contours: %{size: 0.25, start: -4, coloring: "none", end: 1.0, showlines: true},
    line: %{color: "rgba(0, 0, 0, 0.5)", smoothing: 1}
  )
)
|> Figure.add_trace(
  Scatter.new(
    legendgroup: "g1",
    name: "Surface<br>pressure",
    mode: "lines",
    hoverinfo: "skip",
    x: json |> Enum.at(4) |> Map.get("x"),
    y: json |> Enum.at(4) |> Map.get("y"),
    line: %{color: "rgba(255, 0, 0, 0.5)", width: 1, shape: "spline", smoothing: 1},
    fill: "toself",
    fillcolor: "rgba(255, 0, 0, 0.2)"
  )
)
|> Figure.add_trace(
  Scatter.new(
    showlegend: false,
    legendgroup: "g1",
    mode: "lines",
    hoverinfo: "skip",
    x: json |> Enum.at(5) |> Map.get("x"),
    y: json |> Enum.at(5) |> Map.get("y"),
    line: %{color: "rgba(255, 0, 0, 0.3)", width: 1}
  )
)
|> Figure.add_trace(
  Scatter.new(
    showlegend: false,
    legendgroup: "g1",
    name: "cp",
    text: json |> Enum.at(6) |> Map.get("text"),
    mode: "lines",
    hoverinfo: "text",
    x: json |> Enum.at(6) |> Map.get("x"),
    y: json |> Enum.at(6) |> Map.get("y"),
    line: %{color: "rgba(255, 0, 0, 0.2)", width: 0}
  )
)
|> Figure.update_layout(
  title: "Flow over a Karman-Trefftz Airfoil",
  hovermode: "closest",
  height: 700,
  width: 900,
  margin: %{r: 60, b: 40, l: 40, t: 80},
  xaxis: %{
    zeroline: false,
    scaleratio: 1,
    scaleanchor: "y",
    range: [-3.8, 3.8],
    showgrid: false
  },
  yaxis: %{zeroline: false, range: [-1.8, 1.8], showgrid: false}
)
|> Plotly.show()