c3js › value 0 aligned between Y and Y2

问题

How to align the Y 0 axis value to Y2 0 axis value?

See jsFiddle to understand.

I tried the option center:0 on the axe's but i don't want 0 on center of graph..

var chart = c3.generate({
    data: {
        columns: [
            ['data1', 2000, 350, 300, -200, -50, 0],
            ['data2', 130, 100, 140, 200, 150, 50]
        ],
        types: {
            data1: 'line',
            data2: 'bar'
        },
        axes:{
            data1:'y',
          data2:'y2'
        }
    },
    axis: {
        y: {
            padding: {bottom: 0}

        },
         y2: {
                show:true,
            padding: {bottom: 0}

        },
        x: {

            min: 0,
            show: true
        }
    },
    grid: {
        x: {
            show: false
        },
        y: {
            show: false,
            lines: [
                {value: 0.0, text: 'i want 0 here ->', class:'red'}
            ]
        }
    }
});

Official documentation.

Thanks.

回答1:

In general you want the same proportion of the axes ranges above and below zero, which is why min: -20 would work for this particular example

This would work in general after you've generated your chart:

var d1 = d3.extent(chart.data.values("data1"));
var d2 = d3.extent(chart.data.values("data2"));
if (d2[0] < 0 || d1[0] < 0) {
        var prop1 = d1[0] < 0 ? -(d1[1] / d1[0]) : Math.Infinity; 
    var prop2 = d2[0] < 0 ? -(d2[1] / d2[0]) : Math.Infinity;
    if (prop1 > prop2) {
        d1[0] = -(d1[1] / prop2);
    } else {
          d2[0] = -(d2[1] / prop1);
    }
    chart.axis.range({
            min: {y: d1[0], y2: d2[0]},
          max: {y: d1[1], y2: d2[1]}
    });
}

Basically if either (or both) series has a negative value then it scales both series to have the same proportion of positive to negative range using the min/max axis settings. This means zero sits at the same vertical point for both

https://jsfiddle.net/ynz6quum/4/

来源：https://stackoverflow.com/questions/38851558/c3js-value-0-aligned-between-y-and-y2