try the following code :
In your controller :
function myCtrl ($scope) {
$scope.units = [
{'id': 10, 'label': 'test1'},
{'id': 27, 'label': 'test2'},
{'id': 39, 'label': 'test3'},
];
$scope.data= $scope.units[0]; // Set by default the value "test1"
};
In your page :
Working Fiddle