I have a button group with 2 radio buttons: MHz and GHz.
I don't need to run a callback function on selection changes. My GUI also has a "RUN" button. When this is clicked, it goes through a callback routine, where I do want to check the selected value in the button group. I tried this:
BW_units = 1E6;
BW_units = 1E9;
But it did not work. In fact,
The MATLAB document says this is a scalar handle? I am not sure how this works.
Currently selected radio button or toggle button uicontrol in the managed group of components. Use this property to determine the currently selected component or to initialize selection of one of the radio buttons or toggle buttons. By default, SelectedObject is set to the first uicontrol radio button or toggle button that is added. Set it to  if you want no selection. Note that SelectionChangeFcn does not execute when this property is set by the user.