extjs chart problem

I am using ext do draw charts in the browser,I meet a problem:

I want to draw two lines in one chart, so I use the ColumnChart, this is my data:

var store = new Ext.data.JsonStore({
    fields:['name', 'visits', 'views'],
    data: [
        {name:'Jul 07', visits: 245, views: 3000000},
        {name:'Aug 07', visits: 240, views: 3500000},
        {name:'Sep 07', visits: 355, views: 4000000},
        {name:'Oct 07', visits: 375, views: 4200000},
        {name:'Nov 07', visits: 490, views: 4500000},
        {name:'Dec 07', visits: 495, views: 5800000},
        {name:'Jan 08', visits: 520, views: 6000000},
        {name:'Feb 08', visits: 620, views: 7500000}
    ]
});

Since the Visit data is much le开发者_Go百科ss than views.

So the line which respresent the visit is too close to the xaxis, is there any idea?

Thanks for your reply, I decide to make them the same scale. BTW, I have another question,hope you can give some suggesion:

To create yAxis with different scales in ExtJs4 you can use the left and right axis.

xtype: 'chart',
width: 400,
height: 300,
store: myStore,
axes: [
    {
        //title: 'Size',
        type: 'Numeric',
        position: 'left',
        fields: ['sizeInBytes'],
        minimum: 0
    },{ /// NEW yAxis Scale ///
        //title: 'Run Time',
        type: 'Numeric',
        position: 'right',
        fields: ['runTimeMin'],
        minimum: 0
    },{
        //title: 'Date',
        type: 'Time',
        position: 'bottom',
        fields: ['startTime'],
        dateFormat: 'm/d/y h:i A'
    }
],
series: [
    {
        type: 'column',
        axis: 'left',
        xField: 'startTime',
        yField: 'sizeInBytes'
    },{ /// Specify the Axis and data field to use ///
        type: 'line',
        axis: 'right',// <----
        xField: 'startTime',
        yField: 'runTimeMin' // <----
    }
]

As far as I can see there are two options: 1. Add a second Y axis, with a different scale 2. Scale the larger values down

ExtJS charts- to my knowledge- doesnt offer the ability to add a second axis, though there are work arounds (see http://www.sencha.com/forum/showthread.php?72557-Ext-JS-Charts-Second-Y-Axis-Scale)

Therefore the easiest way would be to simply divide the larger values by, say, 10,000 to bring the two scale's inline, then make a note that they are in thousands.