Trying to Program a Switch-Case Expression for a Pop-up Menu in a MATLAB GUI

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Caleb 2012-7-18

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Can someone tell me what's wrong with my syntax or any other errors you spot?

% --- Executes on selection change in popupmenu_filters.
function popupmenu_filters_Callback(hObject, eventdata, handles)
% hObject    handle to popupmenu_filters (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% determine which filter to apply by reading string in pop-up menu
str = get(hObject, 'String');
val = get(hObject, 'Value');
% set current filter to the user-selected filter
switch str{val};
    case 'imdilate' 
        handles.current_filter = imdilate
    case 'imerode'
        handles.current_filter = imerode
    case 'imopen'
        handles.current_filter = imopen
    case 'imclose'
        handles.current_filter = imclose
    case 'imtophat'
        handles.current_filter = imtophat
    case 'imbothat'
        handles.current_filter = imbothat
    case 'entropy filter'
        handles.current_filter = entropyfilt
end
handles.image2 = handles.current_filter(handles.image);
  handles.axes2(imshow(handles.image2));
  % pushbutton_save handles structure
  guidata(hObject, handles);

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Answer 1

Walter Roberson 2012-7-18

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handles.current_filter = @imdilate;

Without the @ it is going to _ call_ imdilate with no arguments.

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Answer 2

Caleb 2012-7-19

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So when I'm adding slider capability to the code, how do I call that within the program. Would it be:

handles.image2 = handles.current_filter(handles.image, [handles.slider1 handles.slider2];

or something like that?

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Caleb 2012-7-23

I'm using R2011b

Caleb 2012-7-23

And using the @function_handle has worked so far. I just haven't been able to apply the changes from the slider to the function.

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Answer 3

Sean de Wolski 2012-7-19

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编辑：Sean de Wolski 2012-7-19

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Rather than using switch I would package this as a cell array of function handles and then extract the value:

ops={@imdilate,@imerode,@imopen} %etc
handles.current_filter = ops{val};

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Caleb 2012-7-19

编辑：Caleb 2012-7-19

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Now it's giving me this error:

Attempted to access handles.axes2(234.013); index must be a positive integer or logical.
Error in FESgui>popupmenu_filters_Callback (line 562)
handles.axes2(imshow(handles.image2));

Even though my handles structure contains handles for axes2

            pushbutton_browse: 238.0118
                        axes2: 233.0125
                        axes1: 228.0066
                     uipanel5: 243.0062
                     uipanel4: 241.0061
                     uipanel3: 239.0079
                     uipanel2: 56.0078