GUI的问题

??? Attempt to reference field of non-structure array.

Error in ==> untitled1>pushbutton1_Callback at 82
zb=str2double(get(handles.edit20,'String'));

Error in ==> gui_mainfcn at 96
        feval(varargin{:});

Error in ==> untitled1 at 42
    gui_mainfcn(gui_State, varargin{:});

Error in ==>
@(hObject,eventdata)untitled1('pushbutton1_Callback',hObject,eventdata,guidata(hObject))

 
??? Error while evaluating uicontrol Callback



我是新手啊  这个是嘛意思