How-To: Customizing Visualizations

Mix.install([
  {:yog_ex, path: "/home/mafinar/repos/elixir/yog_ex"},
  {:kino_vizjs, "~> 0.5.0"}
])

Introduction

Visualizing a graph is often the first step in debugging or communicating a complex algorithm. Yog provides a powerful Yog.Render.DOT engine that transforms your graphs into Graphviz DOT strings, which can be rendered in Livebook using Kino.VizJS.

🎨 Basic Styling

You can provide global attributes to the to_dot/2 function to change the overall look.

g = Yog.Generator.Classic.petersen()

# Change layout direction and node shape
dot = Yog.Render.DOT.to_dot(g, 
  graph_attributes: [rankdir: "LR", bgcolor: "#f8fafc"],
  node_attributes: [shape: "doublecircle", color: "#6366f1", fontname: "Outfit"]
)

Kino.VizJS.render(dot)

✨ Highlighting Paths & Nodes

A common task is to highlight the result of an algorithm (e.g., a shortest path).

g = Yog.Generator.Classic.grid_2d(5, 5)
source = 0
target = 24

{:ok, path} = Yog.Pathfinding.shortest_path(in: Yog.Builder.GridGraph.to_graph(g), from: source, to: target)

# Highlight nodes and edges in the path
dot = Yog.Render.DOT.to_dot(g, 
  highlight_nodes: path.nodes,
  highlight_edges: Enum.chunk_every(path.nodes, 2, 1, :discard) |> Enum.map(fn [u, v] -> {u, v} end)
)

Kino.VizJS.render(dot)

🏷️ Custom Node & Edge Labels

You can provide a mapping or a function to generate labels based on node/edge data.

g = Yog.directed()
  |> Yog.add_node(1, %{name: "Alice", role: "Admin"})
  |> Yog.add_node(2, %{name: "Bob", role: "User"})
  |> Yog.add_edge!(1, 2, %{action: "Deletes"})

# Generate labels from data
node_labels = Map.new(Yog.Model.all_nodes(g), fn id -> 
  data = Yog.Model.node(g, id)
  {id, data.name}
end)

edge_labels = Map.new(Yog.Model.all_edges(g), fn {u, v, weight} -> 
  {{u, v}, weight.action}
end)

dot = Yog.Render.DOT.to_dot(g, 
  node_labels: node_labels,
  edge_labels: edge_labels
)

Kino.VizJS.render(dot)

🏗️ Theming

Yog comes with several built-in themes to quickly switch between styles.

g = Yog.Generator.Classic.binary_tree(3)

# 1. Dark Theme
dot_dark = Yog.Render.DOT.to_dot(g, theme: :dark)
IO.puts "--- Dark Theme ---"
Kino.VizJS.render(dot_dark)

# 2. Minimal Theme
dot_min = Yog.Render.DOT.to_dot(g, theme: :minimal)
IO.puts "--- Minimal Theme ---"
Kino.VizJS.render(dot_min)

Summary

Customizing visualizations in Yog is highly flexible:

1. Global Attributes: Control the layout and background.
2. Highlighting: Bring attention to specific nodes or edges.
3. Data-Driven Labels: Use your actual Elixir data to label the graph.
4. Themes: Use professionally curated presets for a quick premium look.

In the next “How-To”, we’ll look at Importing and Exporting graphs in formats like GraphML and JSON.