Radio Buttons using NSMatrix has been deprecated and information on how to use Radio Buttons without NSMatrix is difficult to find. So this is documentation of a way to use the new Radios Buttons using Xcode 7.2.1 and Swift 2.1.1.
Create a new Xcode project and choose Cocoa Application under OS X Application. Call it Radio Buttons and check Swift. Do not check Use Storyboards, Create Document-Based Application or Use Core Data.