How-To: Importing & Exporting Graphs

Mix.install([
  {:yog_ex, path: "/home/mafinar/repos/elixir/yog_ex"},
  {:jason, "~> 1.4"} # Needed for JSON
])

Introduction

Yog is designed to be a “good citizen” in the data ecosystem. It supports several industry-standard formats for importing and exporting graphs, ensuring that you can easily integrate Yog with other tools like Gephi, Cytoscape, or NetworkX.

📁 GraphML (The Standard)

GraphML is an XML-based format that is the de-facto standard for graph interchange.

g = Yog.Generator.Classic.petersen()

# 1. Export to GraphML string
{:ok, xml} = Yog.IO.GraphML.to_graphml(g)
IO.puts String.slice(xml, 0, 200) <> "..."

# 2. Import from GraphML string
# {:ok, imported_g} = Yog.IO.GraphML.from_graphml(xml)

📄 JSON (For Web & Data)

JSON is perfect for passing graph data to frontend libraries like Cytoscape.js or D3.js.

g = Yog.undirected()
  |> Yog.add_node(1, %{name: "Alice"})
  |> Yog.add_node(2, %{name: "Bob"})
  |> Yog.add_edge!(1, 2, %{type: "friend"})

# 1. Export to JSON (uses Jason internally)
{:ok, json} = Yog.IO.JSON.to_json(g)
IO.puts json

# 2. Import from JSON
{:ok, imported_g} = Yog.IO.JSON.from_json(json)

🛠️ Interoperability with libgraph

If you are migrating from libgraph or need to use an algorithm only available there, Yog makes the transition seamless.

# Create a libgraph graph
lg = Graph.new() |> Graph.add_edge(1, 2)

# Convert to Yog
yg = Yog.IO.Libgraph.from_libgraph(lg)

# Convert back to libgraph
lg_back = Yog.IO.Libgraph.to_libgraph(yg)

🖼️ DOT (For Visualization)

While DOT is primarily for visualization, it is also a valid interchange format.

g = Yog.Generator.Classic.cycle(5)

dot = Yog.Render.DOT.to_dot(g)
IO.puts dot

Summary

Yog‘s I/O suite allows you to:

1. Collaborate: Use GraphML to share data with researchers using other languages.
2. Build: Use JSON to power interactive web visualizations.
3. Migrate: Use the libgraph bridge to leverage existing Elixir codebases.
4. Publish: Use DOT to generate high-quality diagrams.

Next, explore the Gallery to see more exotic graph structures!