C3 Stacked Charting Ordering

It seems as though c3 uses the cumulative values of a row to determine stack ordering.

by davetayls

HTML

<script src="https://rawgit.com/masayuki0812/c3/master/c3.js"></script>
<link rel="stylesheet" href="https://rawgit.com/masayuki0812/c3/master/c3.css">
<div id="chart"></div>

JavaScript

var chart = c3.generate({
    data: {
        columns: [
            ['x', 'first', 'second', 'third'],
            ['a', 10, 20, 70],
            ['b', 80, 40, 1],
            ['c', 10, 40, 29]
        ],
        type: 'area',
        groups: [
            ['a', 'b', 'c']
        ]
    },
    axis: {
        y: {
            padding: {
                top: 0,
                bottom: 0
            },
            max: 100
        }
    },
    grid: {
        y: {
            show: true,
            lines: [{
                value: 0
            }]
        }
    },
    zoom: {
        enabled: true
    }
});