AngularJS directive for C3js line / bar chart

c3LineBar.js

var c3Chart = angular.module('c3Chart', []);
c3Chart.directive('c3LineBar', [function () {
  return{
    restrict : 'A',
    require : 'ngModel',
    link: function (scope,elem,attrs,ngModel) {

      scope.$watch(attrs.ngModel,function(){
        render(scope[attrs.ngModel], elem);
      });

      var render=function(data, elem){

        if(data){
          // apply defaults
          data.color = data.color || 'blue';
          data.chartType = data.chartType || 'bar';

          var thresholdLine = {};
          data.yThreshold = data.yThreshold || false;

          if(data.yThreshold == true){
            thresholdLine.threshold = 'line';
          }

          if(data.x.type == 'timeseries'){
            data.xAxis = data.columns[0][0];
          }
         
          // generate chart
          c3.generate({
            bindto: elem[0],
            color: {
              pattern: [data.color]
            },
            data: {
              x: data.xAxis,
              columns: data.columns,
              type: data.chartType,
              types: thresholdLine
            },
            axis: {
                x: {
                    type: data.x.type,
                    categories: data.x.categories,
                    tick: {
                        format: '%Y-%m-%d'
                    }
                }
            }
          });
        }

      };


    }
  }

}]);