graph in rust using petgraph

August 17, 2019

Getting started with Rust and the petgraph crate, I made a little program to write a graph in “dot” file format. Below is the rust and some command-line code to turn it into a png.

use petgraph::Graph;
use petgraph::dot::{Dot, Config};
use std::fs::File;
use std::io::Write;

fn main() {
    println!("hello graph!");
    let mut graph = Graph::<_, i32>::new();
    graph.add_node("A");
    graph.add_node("B");
    graph.add_node("C");
    graph.add_node("D");
    graph.extend_with_edges(&[
        (0, 1), (0, 2), (0, 3),
        (1, 2), (1, 3),
        (2, 3),
    ]);

    println!("{:?}", Dot::with_config(&graph, &[Config::EdgeNoLabel]));
    let mut f = File::create("example.dot").unwrap();
    let output = format!("{}", Dot::with_config(&graph, &[Config::EdgeNoLabel]));
    f.write_all(&output.as_bytes()).expect("could not write file");
}

output of cargo run:

hello graph!
digraph {
    0 [label="\"A\""]
    1 [label="\"B\""]
    2 [label="\"C\""]
    3 [label="\"D\""]
    0 -> 1
    0 -> 2
    0 -> 3
    1 -> 2
    1 -> 3
    2 -> 3
}

Generate PNG from DOT file

The dot command is part of graphviz, which I installed with brew install graphviz.

The following command creates a PNG file from the .dot file generated by Rust code above

dot -T png -O example.dot

The resulting PNG is displayed at the top-right of this post (next to the Rust code).

---

Special thanks to:
* mcarton’s help on stackoverflow for enlightening me on a bit of Rust nuance as I experimented with petgraph.
* rudifa’s post graphviz-on-the-mac

---