Logarithmic axis - negative values.

[Basts]

Expected behaviour

According to this article, the negative values should be displayed (thanks to this custom code), however, something is broken after the 8.0.4 version.

Last working version: http://jsfiddle.net/BlackLabel/bj3dwe4t/

Actual behaviour

The current version, the negative points are hidden: http://jsfiddle.net/BlackLabel/cdguh2zp/

Product version

Highcharts JS v8.1.2 (2020-06-16)

[pawelfus]

Bisected to commit a31155e - not really helpful. It might be related to the way we refer log2lin and lin2log values. Any ideas @bre1470 ?

[bre1470]

Amazing. I have no idea yet, but I will look into that.

[bre1470]

For me this is the breaking commit: daddf2e

[bre1470]

Okay, so I found the reason. It is not a bug, but just the wrong usage of the axis prototype. If you set the option yAxis.allowNegativeLog to true, everything is working as expected. See: http://jsfiddle.net/u3o2qaw0/

Highcharts.chart('container', {

    title: {
        text: 'Logarithmic axis with custom conversion allows negative values'
    },

    xAxis: {
        categories: ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
            'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
    },

    yAxis: {
        type: 'logarithmic',
        allowNegativeLog: true
    },

    series: [{
        data: [-1000, -100, -10, -1, -0.1, 0, 0.1, 1, 10, 100, 1000]
    }]

});

[bre1470]

@Basts @pawelfus Can you confirm the solution?

[Basts]

@bre1470
Yeah, it seems like the right option to set, however, this option doesn't exist in the API and it doesn't work in the previous versions: http://jsfiddle.net/BlackLabel/bj3dwe4t/, so I think that some update (in the API and article) is required to clearly explain to users how to use it.

[TorsteinHonsi]

Negative values on a log axis is (mathematically) not a thing, and we only keep this hidden option as a convenience so that our demo can work.

Please revert this commit, as we want to keep the footprint as low as possible, and don't need to support backwards compatibility.

[bre1470]

@TorsteinHonsi Please note, that without this change the LogarithmicAxis composition always have redundant conversion functions directly on the axis to allow the demo in its current state to work with ES6. See https://github.com/highcharts/highcharts/blob/master/ts/Core/Axis/LogarithmicAxis.ts#L227-L233