Avoid same points being plotted twice in Google Visualization Chart API

Avoid same points being plotted twice in Google Visualization Chart API References I am plotting a line graph with Google\'s Visualization Chart API, its simply a change in number of leads(an integer) every 30minutes. here what I have done till now: google.load(\"visualization\", \"1\", {packages:[\"corechart\"]}); google.setOnLoadCallback(drawChart); function drawChart() { var jsonData = \'json string goes here\'; var report = $.parseJSON(jsonData); //make it a json object var data = new google.visualization.DataTable(); data.addColumn(\'timeofday\', \'Time\'); data.addColumn(\'number\', \'Leads\'); var interval = 1000 * 60 * 30; //interval of 30mins var graphData = report[\'rush_hour_reports\']; var length = graphData.length; var normalized_data = {}; //placeholder object for(var i=0; i