 trigger: 'axis',
                    axisPointer: {
                        type: 'line'
                    }
                },
                xAxis: {},
                yAxis: {},
                series: [{
                    name: 'no point',
                    type: 'line',
                    data: []
                }, {
                    name: 'one point',
                    type: 'line',
                    data: [[2, 43]]
                }, {
                    name: 'two points',
        