you may see a full code example an app where a chart is updated with new data based on a selection in a release dropdown here. in that code i check if chart exists, and remove it if it does before recreating it:

if (this.down('#mychart')) {
                        xtype: 'rallychart',
                        height: 400,
                        itemid: 'mychart',
                        chartconfig: {
                        chartdata: {
                            categories: schedulestategroups, 
                            series: [ 
                this.down('#mychart')._unmask();  //otherwise loading mask does not go away

Related Query

More Query from same tag