Simple Hierarchical Force (d3 v4; CSV; 72 Lines)

This is the simplest network force diagram I could create. Let me know if you think I can make it tighter.

Build notes:

It pulls data from a csv file. It uses d3.stratify() to reform links into a hierarchy. (NOTE: I ran into a challenge with d.size when moving from json to csv. While size is a feature of my data, I had to now access it from d.data.size.)
To differentiate between local variables and framework objects, I prefix variables with lowercase 'v'.

Not really thes simplest:

I bring data in hiararchically via d3.stratify and translate it back to links--but that's for the benefit of the d3-unconf class I'm teaching.
I've also included tick functionality because it makes me happy to watch it warble into place.

from https://bl.ocks.org/denjn5/6914f73f8bc3f009a875fa2bd11f81d8

<!DOCTYPE html>
<meta charset='utf-8'>
<head>
    <title>Simple Hierarchical Force (d3 v4; CSV; 72 Lines)</title>
    <script src="https://d3js.org/d3.v4.min.js"></script>
</head>

line {
        stroke: #05668D;
        stroke-opacity: 0.3;
        stroke-width: 2px;
    }
</style>

// Prepare our physical space
    var g = d3.select('svg').attr('width', vWidth).attr('height', vHeight).select('g');

// Get the data from our CSV file
    d3.csv('data.csv', function(error, vCsvData) {
        if (error) throw error;

vData = d3.stratify()(vCsvData);
        drawViz(vData);
    });

function drawViz(vData) {
        // Declare d3 layout
        var vLayout = d3.forceSimulation()
            .force('link', d3.forceLink().id(function (d) { return d.id; }))
            .force('charge', d3.forceManyBody())
            .force('center', d3.forceCenter(vWidth / 2, vHeight / 2));

// Layout + Data
        var vRoot = d3.hierarchy(vData);
        var vNodes = vRoot.descendants();
        var vLinks = vRoot.links();

var vLines = g.selectAll('line').data(vLinks).enter().append('line');
        var vCircles = g.selectAll('circle').data(vNodes).enter().append('circle')
            .attr('r', 7);

// Draw on screen
        vLayout.nodes(vNodes).on('tick', ticked);
        vLayout.force('link').links(vLinks);

// Animate on entry.
        function ticked() {
            vLines.attr('x1', function (d) { return d.source.x; })
                .attr('y1', function (d) { return d.source.y; })
                .attr('x2', function (d) { return d.target.x; })
                .attr('y2', function (d) { return d.target.y; });

vCircles.attr('cx', function (d) { return d.x; })
                .attr('cy', function (d) { return d.y; });
        }
    }
</script>

https://d3js.org/d3.v4.min.js