Using Angular ng-show/ng-hide with radio buttons - angularjs

Question

I'm using $scope.checked to show/hide the "Top" text box, name="numRows" in my html.
However, even when I click on the 'top' radio button, $scope.checked always retains the value of `all' when I debug my controller code.
This simply plunker seems to work fine, http://plnkr.co/edit/6GoUZw7zkf8oqUmKg9hf?p=preview, but it won't work in my application.
In the plunker, there's a simple button whose click value will hit the controller event $scope.showval to show the value of either "top" or "all".
My HTML:
<div class="form-group">
<div class="row-fluid">
<label class="col-md-2 col-lg-2 control-label" for="numRows">Returned Rows</label>
<!-- ALL ROWS RADIO -->
<div class="col-md-1 col-lg-1">
<label class="radio-inline" for="radio-all">
<input name="radios" id="radio-all" value="all" type="radio" ng-model="checked" ng-click="setTopRows('all')">All
</label>
</div>
<!-- TOP NUM OF ROWS RADIO -->
<div class="col-md-1 col-lg-1">
<label class="radio-inline" for="radio-top">
<input name="radios" id="radio-top" value="top" type="radio" ng-model="checked" ng-click="setTopRows('top')">Top
</label>
</div>
<!-- NUM OF ROWS TEXT BOX -->
<div class="col-md-2">
<input ng-show="checked == 'top'" ng-hide="checked == 'all'" type="text" class="form-control" name="numRows" ng-model="settings.numRowsReturned" placeholder="" >
</div>
<div class="col-md-3">
Click to show<input type="button" ng-click="showval(e)">
</div>
</div>
</div>
A snippet from my angular controller code :
The $scope.checked value is always 'all', even when I click on 'top' from the html.
(function () {
'use strict';
angular.module('rage')
.controller('GadgetSettingsCtrl_NEW', ['$rootScope', '$scope', '$modalInstance', gridSettings]);
function gridSettings($rootScope, $scope, $modalInstance,) {
var settings = this;
$scope.checked = 'all';
$scope.showval = function (e) {
var test = $scope.checked;
}
$scope.setTopRows = function (numRows) {
if (numRows === 'top') {
$scope.checked = 'top';
}
else {
$scope.checked = 'all';
}
}
function checkOptions(){
var top = '';
if ($scope.checked === 'top') {
top = (settings.numRowsReturned != undefined ? settings.numRowsReturned : '');
}
}
}; // end of gridSettings()
})();
Can someone help me clear up why $scope.checked is NOT changing when I click on the radio buttons ?
thank you,
Bob
****** UPDATE *********
I've added a simple ng-click="setTopRows('all')" to force my scope variable to change. This works, but it seems like too much code to accomplish this.