Made graph2d robust against strings for y values.

docs/graph2d/index.html

@@ -266,7 +266,7 @@ var items = [
         </tr>
         <tr>
             <td>x</td>
-            <td>Number</td>
+            <td>Date</td>
             <td>yes</td>
             <td>Location on the x-axis.</td>
         </tr>

lib/timeline/component/GraphGroup.js

@@ -40,6 +40,10 @@ GraphGroup.prototype.setItems = function(items) {
     if (this.options.sort == true) {
       this.itemsData.sort(function (a,b) {return a.x - b.x;})
     }
+    // typecast all items to numbers. Takes around 10ms for 500.000 items
+    for (var i = 0; i < this.itemsData.length; i++) {
+      this.itemsData[i].y = Number(this.itemsData[i].y);
+    }
   }
   else {
     this.itemsData = [];