Richard - there were changes to how GUI elements are managed around R2014b (I think as I'm still on R2014a - see http://www.mathworks.com/help/matlab/graphics_transition/graphics-handles-are-now-objects-not-doubles.html for details) so what you can code with the later versions is not valid for earlier ones. For older versions, if you have the handle to the control, you would need to use the get function to fetch a specific property. For example, if hText1 is a handle to a text control, then you would do
myText = get(hText1,'String');
to get the string contents within this control which is like what you are doing at
my_field = str2double(get(S.field,'string'));
For the radio button, you would do
my_radio = get(S.radio, 'Value');
