Stacked line chart with negative values

[oettlco]

One-line summary [问题简述]

When i have a line with some negative values (e.g. [3, 1, 2, -1, -3, 1, 3]) and my stack is always 1, i want that the stack also work for "-1" and "-3".

Version & Environment [版本及环境]

• ECharts version [ECharts 版本]: 4
• Browser version: all browsers
• OS Version: all OS

ECharts option [ECharts配置项]

option = {
    xAxis : [
        {
            type: 'category',
        		data: [1,2,3,4,5,6,7,8,9]
        }
    ],
    yAxis : [
        {
            type : 'value'
        }
    ],
    series : [
        {
            name:'stack',
            type:'line',
            stack: 'stack',
            data:[3, 1, 2, -1, -3, 1, 3]
        },
        {
            name:'stack',
            type:'line',
            stack: 'stack',
            areaStyle: {},
            data:[1, 1, 1, 1, 1, 1, 1]
        }
    ]
};

Expected behaviour [期望结果]

I get the following result with the option above.

But i would expect something like this:

Other comments [其他信息]

Example of the bug
https://jsfiddle.net/ykb5n0pa/

[dmichlmayr]

+1

[100pah]

Currently, the stack rule is "positive values stack with positive values, and negative values stack with negative values".

I guess actually you need an "area chart"?
But unfortunately, this type of area chart has not been supported yet.
It should be scheduled.

[oettlco]

Yes, this is exactly what we want. Like the confidence band in the echarts doc but with negative values too.
Is there a plan when something like this could be implemented?

[MINDoSOFT]

Hi everyone!

This would be a very useful feature to have !

Currently you can bypass this problem, by having one series with all the negative values and one series with all the positive values (sharing the same series name). I added an example here as reference. You get an empty space when you switch between the negative and the positive part of the series, but I couldn't find a way to address this.

Best regards,
Sergios.

[h4de5]

btw - we worked around this issue, by drawing a single polygon as custom shape into chart.

as an example we used this code: https://stackoverflow.com/questions/61724715/echarts-plot-the-variance-of-signals

[villebro]

@Ovilia @100pah this is also a feature I would need, and I would be happy to work on it. Is this something the project would be open to merging if I open a PR that maintains backward compatibility but adds this as an alternative option? If so, what would be the preferred API change for enabling this? Also, if there's a good way of working around this I'm happy to add docs/examples so others can do this more easily in the future.

[pissang]

@villebro It will be great! Thanks for picking this up. I think proving a config like stackStrategy is an option.