//so your widgets probably looks like this in your controller.
$scope.standardItems = [
{ sizeX: 2, sizeY: 1, row: 0, col: 0 },
{ sizeX: 2, sizeY: 2, row: 0, col: 2 },
{ sizeX: 1, sizeY: 1, row: 0, col: 4 },
{ sizeX: 1, sizeY: 1, row: 0, col: 5 },
{ sizeX: 2, sizeY: 1, row: 1, col: 0 },
{ sizeX: 1, sizeY: 1, row: 1, col: 4 },
{ sizeX: 1, sizeY: 2, row: 1, col: 5 },
{ sizeX: 1, sizeY: 1, row: 2, col: 0 },
{ sizeX: 2, sizeY: 1, row: 2, col: 1 },
{ sizeX: 1, sizeY: 1, row: 2, col: 3 },
{ sizeX: 1, sizeY: 1, row: 2, col: 4 }
];
//and where ever you want (in controller I mean) - you can do like this:
$scope.standardItemems[3].sizeX = 6;
$scope.standardItemems[3].sizeY = 6;
<div gridster>
<ul>
<li gridster-item="item" ng-repeat="item in standardItems"></li>
</ul>
</div>