Google Gauge plugin for ThingSpeak

<script type='text/javascript' src='https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js'></script>
<script type='text/javascript' src='https://www.google.com/jsapi'></script>
<script type='text/javascript'>

  // set your channel id here
  var channel_id = 21261;
  // set your channel's read api key here if necessary
  var api_key = 'API_HERE';
  // minimum value for the gauge
  var min_gauge_value = -10;
  // maximum value for the gauge
  var max_gauge_value = 40;
  // red range starting point for the gauge
  var red_from = 30;
  // red range ending point for the gauge
  var red_to = 40;
  // blue range starting point for the gauge
  var blue_from = -10;
  // blue range ending point for the gauge
  var blue_to = 0;
  // major ticks
  var major_ticks = ['-10','0','10','20','30','40'];
  // name of the gauge
  var gauge_name = '°C';

  // global variables
  var chart, charts, data;

  // load the google gauge visualization
  google.load('visualization', '1', {packages:['gauge']});
  google.setOnLoadCallback(initChart);

  // display the data
  function displayData(point) {
    data.setValue(0, 0, gauge_name);
    data.setValue(0, 1, point);
    chart.draw(data, options);
  }

  // load the data
  function loadData() {
    // variable for the data point
    var p;

    // get the data from thingspeak
    $.getJSON('https://api.thingspeak.com/channels/' + channel_id + '/feed/last.json?api_key=' + api_key, function(data) {

      // get the data point
      p = data.field2;

      // if there is a data point display it
      if (p) {
        p = Math.round(p * 10)/10;
        displayData(p);
      }
    });
  }

  // initialize the chart
  function initChart() {

    data = new google.visualization.DataTable();
    data.addColumn('string', 'Label');
    data.addColumn('number', 'Value');
    data.addRows(1);

    chart = new google.visualization.Gauge(document.getElementById('gauge_div'));
    options = {width: 200, height: 200, min: min_gauge_value, max: max_gauge_value, redFrom: red_from, redTo: red_to, yellowFrom: blue_from, yellowTo: blue_to, yellowColor: "#7f7fff", minorTicks: 5, majorTicks: major_ticks};

    loadData();

    // load new data every 15 seconds
    setInterval('loadData()', 15000);
  }

</script>