กด checkbox แล้วให้มาร์คเกอร์ขึ้นตามกลุ่ม google maps

<script type="text/javascript">
    //<![CDATA[

    var customIcons = {
      "01": {
        icon: 'http://labs.google.com/ridefinder/images/mm_20_purple.png',
        shadow: 'http://labs.google.com/ridefinder/images/mm_20_shadow.png'
      },
      "02": {
        icon: 'http://labs.google.com/ridefinder/images/mm_20_green.png',
        shadow: 'http://labs.google.com/ridefinder/images/mm_20_shadow.png'
      },
	  "03": {
        icon: 'http://labs.google.com/ridefinder/images/mm_20_blue.png',
        shadow: 'http://labs.google.com/ridefinder/images/mm_20_shadow.png'
      },
	  "04": {
        icon: 'http://labs.google.com/ridefinder/images/mm_20_brown.png',
        shadow: 'http://labs.google.com/ridefinder/images/mm_20_shadow.png'
      }
    };
    var markerGroups = { "01": [], "02": [] , "03": [] , "04": [] }; 
    function load() {
      var map = new google.maps.Map(document.getElementById("map"), {
        center: new google.maps.LatLng(13.754059,100.493317),
        zoom: 13,
        mapTypeId: 'roadmap'
      });
      var infoWindow = new google.maps.InfoWindow;

      // Change this depending on the name of your PHP file
      downloadUrl("dbxml.php", function(data) {
        var xml = data.responseXML;
        var markers = xml.documentElement.getElementsByTagName("marker");
        for (var i = 0; i < markers.length; i++) {
          var name_place = markers[i].getAttribute("name_place");
          var id_category = markers[i].getAttribute("id_category");
          var point = new google.maps.LatLng(
              parseFloat(markers[i].getAttribute("latitude")),
              parseFloat(markers[i].getAttribute("longitude")));
       
		  var html = "<b>" + name_place ;
          var icon = customIcons[id_category] || {};
          var marker = new google.maps.Marker({
            map: map,
            position: point,
            icon: icon.icon,
            shadow: icon.shadow
          });
          bindInfoWindow(marker, map, infoWindow, html);
        }
      });
    }

    function bindInfoWindow(marker, map, infoWindow, html) {
      google.maps.event.addListener(marker, 'click', function() {
        infoWindow.setContent(html);
        infoWindow.open(map, marker);
      });
    }
	function toggleGroup(id_category) {  // marker ตามกลุ่ม
   for (var i = 0; i < markerGroups[id_category].length; i++) {
    var marker = markerGroups[id_category][i];
    if (marker.isHidden()) {
      marker.show();
    } else {
      marker.hide();
    }
  } 
}

    function downloadUrl(url, callback) {
      var request = window.ActiveXObject ?
          new ActiveXObject('Microsoft.XMLHTTP') :
          new XMLHttpRequest;

      request.onreadystatechange = function() {
        if (request.readyState == 4) {
          request.onreadystatechange = doNothing;
          callback(request, request.status);
        }
      };

      request.open('GET', url, true);
      request.send(null);
    }

    function doNothing() {}

    //]]>

  </script>

<label>
        <input type="checkbox" id="01"  onclick="toggleGroup('01')"CHECKED/>
        </label>
      01 
      <label>
      <input type="checkbox" id="02"  onclick="toggleGroup('02')" CHECKED/>
      </label>
      02 
      <label>
      <input type="checkbox" id="03"  onclick="toggleGroup('03')" CHECKED/>
      </label>
      03 
      <label>
      <input type="checkbox" id="04" onclick="toggleGroup('04')" CHECKED/>
      </label>
      04