g2 = new Dygraph(document.getElementById("graphdiv2"),
		 [], // path to CSV file
		 { labels: [],
		   title: "Correlation numbers" }          // options
		);

document.getElementById('dropdown').
    addEventListener('change', function(e) {
	var index = this.value.split(".");
	$.getJSON("_data",
		  {i: index[0], s: index[1], t: index[2]},
		  function(data){
		      var newdata = data["data"].map(function(e){
			  f = e.slice(1);
			  f.unshift(new Date(e[0]));
			  return f});
		      g2.updateOptions({'file': newdata, 'labels': data['labels']});
		  });
    });
var event = new Event('change');
document.getElementById('dropdown').dispatchEvent(event);