如何在ng-class中正确使用ng-init

I have a row of buttons and want to initialize the first button as active (as the data associated with it is loaded in my controller's init function). The below HTML works great, but when I click the other two buttons the 'active' class remains on the first button. I want this button set as active on page load and then treated 'normally' (ie: if a different button is clicked remove active class from first button):I have a row of buttons and want to initialize