MATLAB: Help with SelectionChangeFcn (or how to define the callback function to trigger a specific response)

callbackselectionchangefcnuibuttongroup

Hi, I'm not a great expert with uicontrols and more specifically with uibuttongroups and I need some help.
The thing is I've defined a buttongroup with three radiobuttons linked to it:
dpb = uibuttongroup('FontSize',12,'Position',[.015 .65 .17 .28]);
u0 = uicontrol(dpb,'Style','radiobutton','String','P-130',...
    'Position',[30 110 100 30],'BackgroundColor',[.8,.8,.8],'Tag','1');
u1 = uicontrol(dpb,'Style','radiobutton','String','FAST',...
    'Position',[30 65 100 30],'BackgroundColor',[.8,.8,.8],'Tag','2');
u2 = uicontrol(dpb,'Style','radiobutton','String','SLOW',...
    'Position',[30 20 100 30],'BackgroundColor',[.8,.8,.8],'Tag','3');
Then I added some properties to the uibuttongroup:
set(dpb,'SelectedObject',[]);  % No selection
set(dpb,'SelectionChangeFcn',@dpbcbk); %Deceleration profile's callback
In other part of my script I've created a edit uicontrol (pdp is a uipanel which is parented to) that I want to be updated with a given value depending on the user selection of the aforementioned uibuttongroup:
edt4 = uicontrol(pdp,'Style','edit','Position',[330 200 80 20]);
My problem is to define properly the callback function to get this done. I've tried it (although to no avail) with the following callback:
function dpbcbk(source,eventdata)
switch get(eventdata.NewValue,'tag') 
    case '1'     
        set(edt4,'String','130');
    case '2'        
        set(edt4,'String','150');
    case '3'  
        set(edt4,'String','110');    
end
This are the error messages I get:
Undefined function or variable 'edt4'.
Error in dpbcbk (line 8)
        set(edt4,'String','110');
Error in hgfeval (line 63)
        feval(fcn{1},varargin{:},fcn{2:end});
Error in uitools.uibuttongroup/childAddedCbk>manageButtons (line 79)
    hgfeval(cbk, source, evdata);
I know that there is something that I'm missing, but I don't know much about how to work with callbacks. Any input is welcome.

Best Answer

Ismael - you can try nesting your callback within your function that creates the GUI. A benefit of nested functions is that they have access to the local variables within the "main" function. Try the following
 function build_GUI
     % create the figure
     hFig = figure('Position',[0 0 968 542]);
     % create the button group
     dpb  = uibuttongroup('FontSize',12,'Position',[.015 .65 .17 .28]);
     % add the radio buttons to the button group
     u0 = uicontrol(dpb,'Style','radiobutton','String','P-130',...
        'Position',[30 110 100 30],'BackgroundColor',[.8,.8,.8],'Tag','1');
     u1 = uicontrol(dpb,'Style','radiobutton','String','FAST',...
        'Position',[30 65 100 30],'BackgroundColor',[.8,.8,.8],'Tag','2');
     u2 = uicontrol(dpb,'Style','radiobutton','String','SLOW',...
        'Position',[30 20 100 30],'BackgroundColor',[.8,.8,.8],'Tag','3');
     % set the callbacks
     set(dpb,'SelectedObject',[]);  % No selection
     set(dpb,'SelectionChangeFcn',@dpbcbk); %Deceleration profile's callback
     % do other stuff
     % create the edit box (note hFig being used instead of your pdp)
     edt4 = uicontrol(hFig,'Style','edit','Position',[330 200 80 20]);
     % define the (nested) button group callback
     function dpbcbk(source,eventdata)
        switch get(eventdata.NewValue,'tag') 
            case '1'     
                set(edt4,'String','130');
            case '2'        
                set(edt4,'String','150');
            case '3'  
                set(edt4,'String','110');    
        end
     end  % end for dpbcbk
 end % end for build_GUI
Now, the SelectionChangeFcn callback, which hasn't changed, has access to the edt4 handle, a local variable of build_GUI, and can update this control.
Try the above and see what happens!
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