diff --git a/lib/timeline/component/GraphGroup.js b/lib/timeline/component/GraphGroup.js
index 458fac61..c1326e65 100644
--- a/lib/timeline/component/GraphGroup.js
+++ b/lib/timeline/component/GraphGroup.js
@@ -30,6 +30,17 @@ function GraphGroup(group, groupId, options, groupsUsingDefaultStyles) {
 }
 
 
+function insertionSort (a,compare) {
+  for (var i = 0; i < a.length; i++) {
+    var k = a[i];
+    for (var j = i; j > 0 && compare(k,a[j - 1])<0; j--) {
+      a[j] = a[j - 1];
+    }
+    a[j] = k;
+  }
+  return a;
+}
+
 /**
  * this loads a reference to all items in this group into this group.
  * @param {array} items
@@ -38,13 +49,9 @@ GraphGroup.prototype.setItems = function (items) {
   if (items != null) {
     this.itemsData = 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);
+      insertionSort(this.itemsData,function (a, b) {
+        return a.x > b.x ? 1 : -1;
+      });
     }
   }
   else {
diff --git a/lib/timeline/component/LineGraph.js b/lib/timeline/component/LineGraph.js
index 7a1d8cc9..52bd9ebd 100644
--- a/lib/timeline/component/LineGraph.js
+++ b/lib/timeline/component/LineGraph.js
@@ -455,20 +455,35 @@ LineGraph.prototype._updateAllGroupData = function () {
   if (this.itemsData != null) {
     var groupsContent = {};
     var items = this.itemsData.get();
+    //pre-Determine array sizes, for more efficient memory claim
+    var groupCounts = {};
     for (var i = 0; i < items.length; i++) {
       var item = items[i];
       var groupId = item.group;
       if (groupId === null || groupId === undefined) {
         groupId = UNGROUPED;
       }
-      if (groupsContent[groupId] === undefined) {
-        groupsContent[groupId] = [];
+      groupCounts.hasOwnProperty(groupId) ? groupCounts[groupId]++ : groupCounts[groupId] = 1;
+    }
+    //Now insert data into the arrays.
+    for (var i = 0; i < items.length; i++) {
+      var item = items[i];
+      var groupId = item.group;
+      if (groupId === null || groupId === undefined) {
+        groupId = UNGROUPED;
       }
+      if (!groupsContent.hasOwnProperty(groupId)) {
+        groupsContent[groupId] = new Array(groupCounts[groupId]);
+      }
+      //Copy data (because of unmodifiable DataView input.
       var extended = util.bridgeObject(item);
       extended.x = util.convert(item.x, 'Date');
       extended.orginalY = item.y; //real Y
-      extended.y = item.y;
-      groupsContent[groupId].push(extended);
+      // typecast all items to numbers. Takes around 10ms for 500.000 items
+      extended.y = Number(item.y);
+
+      var index= groupsContent[groupId].length - groupCounts[groupId]--;
+      groupsContent[groupId][index] = extended;
     }
     //Update legendas, style and axis
     for (var groupId in groupsContent) {