I'm a professor of mathematics at the University of North Carolina Asheville. I've also done a fair amount of consulting work over the years focusing on scientific and data visualization.
I'm happy to be part of the first Observable Ambassador's cohort.
doit = color_nodes()
async function color_nodes() {
let job_id = job_list.length;
job_list.forEach((_, i) => (job_list[i] = false));
job_list.push(true);
d3.select(comment).text("");
d3.select(greedy_animation)
.selectAll("g.node")
.select("ellipse")
.attr("fill", "white");
let colored_nodes = d3.range(G.nodes.length).map((n) => ({
idx: n,
neighbors: neighbors(G, n)
}));
// The order of the nodes can make a difference.
// colored_nodes = d3.sort(colored_nodes, (n) => n.neighbors.length);
let current_color = 1;
let cnt = 0;
for (
let i = 0;
i < colored_nodes.length && cnt < colored_nodes.length && job_list[job_id];
i++
) {
d3.select(comment).text(`Setting color ${current_color}.`);
await Promises.delay(200);
let node1 = colored_nodes[i];
if (test(node1, current_color)) {
node1.color = current_color;
cnt++;
d3.select(greedy_animation)
.select(`g#node${node1.idx + 1}`)
.select("ellipse")
.attr("fill", d3.schemeCategory10[current_color]);
for (let j = i + 1; j < colored_nodes.length && job_list[job_id]; j++) {
await Promises.delay(100);
let node2 = colored_nodes[j];
if (test(node2, current_color)) {
node2.color = current_color;
cnt++;
d3.select(greedy_animation)
.select(`g#node${node2.idx + 1}`)
.select("ellipse")
.attr("fill", d3.schemeCategory10[current_color]);
}
}
current_color++;
}
}
d3.select(comment).text(`Graph successfully ${current_color - 1}-colored!`);
function test(node, c) {
return (
!node.color &&
node.neighbors.every(function (k) {
let neighbor = colored_nodes.filter((node) => node.idx == k)[0];
return !neighbor.color || neighbor.color != c;
})
);
}
}
G = {
again;
if (type == "Graph") {
return random_graph(15, 0.2);
} else {
return random_tree(0.6);
}
}
function neighbors(G, node) {
let nodes = G.edges
.filter((e) => e.source == node || e.target == node)
.map((e) => [e.source, e.target])
.flat()
.filter((n) => n != node);
return nodes;
}
function random_graph(n, p) {
let edges = d3
.range(n)
.map((i) =>
d3
.range(i + 1, n)
.map((j) =>
d3.randomUniform(0, 1)() < p ? { source: i, target: j } : []
)
)
.flat(2);
return { nodes: d3.range(n), edges };
}
function random_tree(p) {
let cnt = 0;
let root = { id: cnt++, depth: 0, children: [] };
let stack = [root];
let edges = [];
while (stack.length > 0 && cnt < 10000) {
let node = stack.pop();
let depth = node.depth;
for (let i = 0; i < 3; i++) {
if (d3.randomUniform(0, 1)() < p ** node.depth) {
let child = { id: cnt++, depth: node.depth + 1, children: [] };
node.children.push(child);
stack.push(child);
edges.push({ source: node.id, target: child.id });
}
}
}
return { nodes: d3.range(cnt), edges };
}
job_list = []
dot`graph{rankdir="LR"; ${random_graph(5, 0.5)
.edges.map((e) => `${e.source}--${e.target}`)
.join(";")}}`
dot`graph{rankdir="LR"; node[shape=point]; ${random_graph(7, 0.5)
.edges.map((e) => `${e.source}--${e.target}`)
.join(";")}}`
dot`graph{${rg}}`
rg = random_graph(10, 0.4)
.edges.map((e) => `${e.source}--${e.target}`)
.join(";")
One platform to build and deploy the best data apps
Experiment and prototype by building visualizations in live JavaScript notebooks. Collaborate with your team and decide which concepts to build out.
Use Observable Framework to build data apps locally. Use data loaders to build in any language or library, including Python, SQL, and R.
Seamlessly deploy to Observable. Test before you ship, use automatic deploy-on-commit, and ensure your projects are always up-to-date.