http://lua-api.factorio.com/latest/LuaGuiElement.html
mentions both radiobutton and radio-button.
[Rseding91] Wrong documentation: radiobutton not radio-button
Re: [Rseding91] Wrong documentation: radiobutton not radio-button
Thanks for noticing. It's now fixed for the next version of 0.15.
If you want to get ahold of me I'm almost always on Discord.