Highcharts - best way to handle and display zero (or negative) values in a line chart series with logarithmic Y axis

Question

In my HighChart line graphs, the series data is being fed from my Ruby on Rails application dynamically. Sometimes the series values are zeros or less which is a problem for HighCharts and it throws the following exception:

Highcharts Error #10
Can't plot zero or subzero values on a logarithmic axis

So as a work-around, I process my ruby array to conditionally replace a zero of less value with an insignificant positive number, .e.g. 0.00001 as shown below:

oil_vol_array = d_array[1].map { |e| (e < 0.0001) ? 0.0001 : e.round(3) }

This prevents the exception being thrown, but the display shows the graph starting at 0.0001 if the starting value is zero (understandably so, since I asked it to). A more desirable display would be to start the graph at zero, but HighChart doesn't like it :(

Is there a way that this can be achieved?

Answer 1

Have you tried using a label formatter?

var chart = new Highcharts.Chart({ 
    yAxis: {        
        labels: {
            formatter: function() {
                if(this.value === 0.00001){
                    return 0;
                } else {
                    return this.value;
                }
            }
        }
    }
});

Answer 2

When dealing with huge numbers, it's better to use the standard label formatter for values other than 0, otherwise your labels gonna be displayed like this: 1000000000... To change this replace 'else' statement to the call to the original label formatter method below:

var chart = new Highcharts.Chart({ 
    yAxis: {        
        labels: {
            formatter: function() {
                if(this.value === 0.00001){
                    return 0;
                } else {
                    return Highcharts.Axis.prototype.defaultLabelFormatter.call(this);
                }
            }
        }
    }
});