动态X轴问题echarts 折线配置项内容和展示

假如两条折线，一条data7,8,9另一条5,6,7,8,9. 其中7,8,9的X轴相对应的应该是5,6,7 可现在对应的是1,2,3 现在我想通过选择legend。改变X轴的坐标。

      option = {
    title: {
        text: 'Awesome Chart'
    },
    grid: {
        left: 45,
        top: 60,
        right: 20,
        bottom: 100
    },
    tooltip: {
        trigger: 'axis'
    },
    legend: {
        selectedMode: 'single',
        top: 230,
        //    	    	bottom:20,
        left: 'center',
        itemWidth: 0,
        itemGap: 0,
        data: [{
            name: '轻油',
            icon: 'none',
        }, {
            name: '重油',
            icon: 'none',
        }],
    },
    xAxis: {
        data: [1, 2, 3, 4, 5, 6, 7]
    },
    yAxis: {},
    series: [{
        name: '轻油',
        type: 'line',
        data: [null, null, null, null, 7, 8, 9],
        showSymbol: false,
        smooth: true,
    }, {
        name: '重油',
        type: 'line',
        data: [5, 6, 7, 8, 9, 10],
        showSymbol: false,
        smooth: true,
    }, ]
};