coreplot 1.2 中固定x，y轴的位置

参考文档

http://stackoverflow.com/questions/7684334/iphone-sdk-core-plot-how-to-display-y-axis-on-the-right-side-on

CPTXYAxisSet* axisSet = (CPTXYAxisSet *)graph.axisSet; //1 获取图纸对象的坐标系；    //固定xy轴的显示位置    axisSet.yAxis.axisConstraints = [CPTConstraints constraintWithRelativeOffset:0.0];    axisSet.xAxis.axisConstraints = [CPTConstraints constraintWithRelativeOffset:0.0];    //Y的坐标系显示在右边    graph.plotAreaFrame.paddingRight = 20.0f;