Simple GUI not working, error Varagout feval(...

hello, I am relatively new to matlab and am trying to teach myself how to create and use GUIs. I am working on a simple test GUI that simply plots a 3D graph. However I cannot seem to get the popup menu to work. I get the following errors and am not sure what they mean.

??? Reference to non-existent field 'output'.

Error in ==> TESTGUI1>TESTGUI1_OutputFcn at 79
varargout{1} = handles.output;

Error in ==> gui_mainfcn at 265
        feval(gui_State.gui_OutputFcn, gui_hFigure, [],
        gui_Handles);

Error in ==> TESTGUI1 at 42
    gui_mainfcn(gui_State, varargin{:});

Not sure what this all means as it was code that came pre-coded into the GUI guide. Any suggestions? I have pasted a copy of my code below if that helps. THANKS!

Dan

function varargout = TESTGUI1(varargin)
% TESTGUI1 MATLAB code for TESTGUI1.fig
%      TESTGUI1, by itself, creates a new TESTGUI1 or raises the existing
%      singleton*.
%
%      H = TESTGUI1 returns the handle to a new TESTGUI1 or the handle to
%      the existing singleton*.
%
%      TESTGUI1('CALLBACK',hObject,eventData,handles,...) calls the local
%      function named CALLBACK in TESTGUI1.M with the given input arguments.
%
%      TESTGUI1('Property','Value',...) creates a new TESTGUI1 or raises the
%      existing singleton*.  Starting from the left, property value pairs are
%      applied to the GUI before TESTGUI1_OpeningFcn gets called.  An
%      unrecognized property name or invalid value makes property application
%      stop.  All inputs are passed to TESTGUI1_OpeningFcn via varargin.
%
%      *See GUI Options on GUIDE's Tools menu.  Choose "GUI allows only one
%      instance to run (singleton)".
%
% See also: GUIDE, GUIDATA, GUIHANDLES

% Edit the above text to modify the response to help TESTGUI1

% Last Modified by GUIDE v2.5 19-Jan-2012 13:32:40

% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @TESTGUI1_OpeningFcn, ...
                   'gui_OutputFcn',  @TESTGUI1_OutputFcn, ...
                   'gui_LayoutFcn',  [] , ...
                   'gui_Callback',   []);
if nargin && ischar(varargin{1})
    gui_State.gui_Callback = str2func(varargin{1});
end

if nargout
    [varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
    gui_mainfcn(gui_State, varargin{:});
end
% End initialization code - DO NOT EDIT

% --- Executes just before TESTGUI1 is made visible.
function TESTGUI1_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% varargin   command line arguments to TESTGUI1 (see VARARGIN)

% Choose default command line output for TESTGUI1
handles.peaks=peaks(35);
handles.membrane=membrane;
[x,y]=meshgrid(-8:0.5:8);
r=sqrt(x.^2+y.^2)+eps;
sinc=sin(r)./r;
handles.sinc=sinc;
handles.current_data=handles.peaks;
surf(handles.current_data);
% Update handles structure
guidata(hObject, handles);

% UIWAIT makes TESTGUI1 wait for user response (see UIRESUME)
% uiwait(handles.figure1);

% --- Outputs from this function are returned to the command line.
function varargout = TESTGUI1_OutputFcn(hObject, eventdata, handles) 
% varargout  cell array for returning output args (see VARARGOUT);
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Get default command line output from handles structure
varargout{1} = handles.output;

% --- Executes on selection change in popupmenu1.
function popupmenu1_Callback(hObject, eventdata, handles)
% hObject    handle to popupmenu1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: contents = cellstr(get(hObject,'String')) returns popupmenu1 contents as cell array
%        contents{get(hObject,'Value')} returns selected item from popupmenu1

val=get(hObject,'Value');
str=get(hObject,'String');
switch str(val)
    case 'Peaks' %user selects peaks
        handles.current_data=handles.peaks;
    case 'Membrane' %User selects membrane
        handles.current_data=handles.membrane;
    case 'Sinc' %User selects sinc
        handles.current_data=handles.sinc;
end
guidata(hObjects,handles);

% --- Executes during object creation, after setting all properties.
function popupmenu1_CreateFcn(hObject, eventdata, handles)
% hObject    handle to popupmenu1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: popupmenu controls usually have a white background on Windows.
%       See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
    set(hObject,'BackgroundColor','white');
end

% --- Executes on button press in Pushbutton1.
function Pushbutton1_Callback(hObject, eventdata, handles)
% hObject    handle to Pushbutton1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

%Display Surface Plot of the Currently Selected data
surf(handles.current_data);

% --- Executes on button press in pushbutton2.
function pushbutton2_Callback(hObject, eventdata, handles)
% hObject    handle to pushbutton2 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

%Display Mesh Plot of the Currently Selected data
mesh(handles.current_data);

% --- Executes on button press in pushbutton3.
function pushbutton3_Callback(hObject, eventdata, handles)
% hObject    handle to pushbutton3 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

%Display Contour Plot of the Currently Selected data
contour(handles.current_data);

THANKS Again for your help!

Answer 1

[Walter Roberson]

In TESTGUI1_OpeningFcn, change the line

surf(handles.current_data);

to

handles.output = surf(handles.current_data);