how to call data in watch group only once even though mulitple value are changing?

I have a $watchgroup in angularjs in which I have two values, primaryApplicationChartData and secondaryApplicationChartData.
The watchgroup gets called when both of them change.

I want to make sure that the code inside $watchgroup i.e., drawStockChart() func gets called only once even though both chart data change.

Can anyone give some idea on how to do it?

Thanks.

scope.$watchGroup(['primaryApplicationChartData', 'secondaryApplicationChartData'], function(newValues, oldValues, scope) {
        console.log("chartData has changed");
        drawStockChart();
});

Source: AngularJS