Source: directives/heatmap-layer.js

/**
 * @ngdoc directive
 * @name heatmap-layer
 * @requires Attr2Options 
 * @description 
 *   Requires:  map directive
 *   Restrict To:  Element
 *
 * @example
 * Example: 
 *
 *   <map zoom="11" center="[41.875696,-87.624207]">
 *     <heatmap-layer data="taxiData"></heatmap-layer>
 *   </map>
 */
(function() {
  'use strict';

  angular.module('ngMap').directive('heatmapLayer', ['Attr2Options', '$window', function(Attr2Options, $window) {
    var parser = Attr2Options;
    
    return {
      restrict: 'E',
      require: '^map',

      link: function(scope, element, attrs, mapController) {
        var filtered = parser.filter(attrs);

        /**
         * set options 
         */
        var options = parser.getOptions(filtered);
        options.data = $window[attrs.data] || scope[attrs.data];
        if (options.data instanceof Array) {
          options.data = new google.maps.MVCArray(options.data);
        } else {
          throw "invalid heatmap data";
        }
        var layer = new google.maps.visualization.HeatmapLayer(options);

        /**
         * set events 
         */
        var events = parser.getEvents(scope, filtered);
        console.log('heatmap-layer options', layer, 'events', events);

        mapController.addObject('heatmapLayers', layer);
      }
     }; // return
  }]);
})();