Simple Treemap (d3 v4; CSV; 52 Lines)

This is the simplest treemap 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'.
The .paddingOuter(5) highlights the hierachical grouping. Normally this is achieved via different colors in treemaps.

From https://bl.ocks.org/denjn5/bb835c4fb8923ee65a13008832d2efed

<!DOCTYPE html>
<meta charset="utf-8">
<head>
    <title>Simple Treemap (d3 v4; CSV; 52 Lines)</title>
    <script src="https://d3js.org/d3.v4.min.js"></script>
</head>

// 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.treemap().size([vWidth, vHeight]).paddingOuter(5);

// Layout + Data
        var vRoot = d3.hierarchy(vData).sum(function (d) { return d.data.size; });
        var vNodes = vRoot.descendants();
        vLayout(vRoot);
        var vSlices = g.selectAll('rect').data(vNodes).enter().append('rect');

// Draw on screen
        vSlices.attr('x', function (d) { return d.x0; })
            .attr('y', function (d) { return d.y0; })
            .attr('width', function (d) { return d.x1 - d.x0; })
            .attr('height', function (d) { return d.y1 - d.y0; });
    }
</script>

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