How to make the ionic radio toggle on/off?

I want the user to be able to toggle one option. If they toggle to another option within a section, it will toggle the other previously made selection to off. A user will also be able to deselect their selection (i.e). Steps:-

1. Tap button 1(button 1 turns "off" to "on")
2. Tap button 1 again(it should turn "On" to "Off")

I used the following code

    app.directive('kmItoggleRadio', function() {
  return{
    restrict:'E',
    compile: function(element,attrs) 
    {
      var leftTitle='';
            if(angular.isUndefined(attrs.kmLeftTitle)) {
               leftTitle='';
            }
            else {
                leftTitle=attrs.kmLeftTitle;
            }
      var rightTitle='';
            if(angular.isUndefined(attrs.kmRightTitle)) {
               rightTitle='';
            }
            else {
                rightTitle="  "+attrs.kmRightTitle ;
            }
      var show='false';
            if(angular.isUndefined(attrs.kmShow)) {
              show="true";
            }
            else {
              show=attrs.kmShow;
            }

      var htmlText='<div><div ng-switch on="format">'+
            '<div ng-switch-when="kmForm">'+
            '<div ng-show='+show+'>'+
            '<ul class="list">'+
            '<li class="item item-toggle">'+
            ''+leftTitle+''+
            '<label class="toggle toggle-positive">'+
            '<input type="radio" value="'+attrs.kmValue+'" ng-model="'+attrs.kmModel+'" >'+
            '<div class="track">'+
            '<div class="handle"></div>'+
            '</div>'+
            '</label>'+
            '</ul>'+
            '</div>'+
            '</div>'+
            '<div ng-switch-when="kmPreview">'+
            '<div ng-show='+show+'>'+
            '<ul class="list">'+
            '<li class="item item-toggle">'+
            ''+leftTitle+''+
            '<label class="toggle toggle-positive">'+
            '<input type="checkbox" disabled="true" value="'+attrs.kmValue+'" ng-model="'+attrs.kmModel+'">'+
            '<div class="track">'+
            '<div class="handle"></div>'+
            '</div>'+
            '</label>'+
            '</ul>'+
            '</div>'+
            '</div>'+
            '</div></div>';
            element.replaceWith(htmlText);
    }
  }
})

In HTML

<km-itoggle-radio  km-model="a.c" km-value="d" km-left-title="Dhoni"></km-itoggle-radio>
<km-itoggle-radio  km-model="a.c" km-value="s" km-left-title="Kohli"></km-itoggle-radio>

I want to know how to make the radio button toggle on/off by tapping the button again (with out tapping the other button in same group).