function varargout = tls(varargin)
% TLS -- Transmission Line Simulator
% Simulates a lossless transmission line.  Given appropriate input values,
% the TLS GUI will calculate the associated output values.
% Various plots, including an animated plot, can be selected by the user.
%
% Copyright (c) 2005, C. H. G. Wright and R. G. Jacquot
% Version 1.13     Last modified on 20 May 2005


% M-file for tls.fig
%      TLS, by itself, creates a new TLS or raises the existing
%      singleton*.
%
%      H = TLS returns the handle to a new TLS or the handle to
%      the existing singleton*.
%
%      TLS('CALLBACK',hObject,eventData,handles,...) calls the local
%      function named CALLBACK in TLS.M with the given input arguments.
%
%      TLS('Property','Value',...) creates a new TLS or raises the
%      existing singleton*.  Starting from the left, property value pairs are
%      applied to the GUI before tls_OpeningFunction gets called.  An
%      unrecognized property name or invalid value makes property application
%      stop.  All inputs are passed to tls_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

% Copyright 2002-2003 The MathWorks, Inc.

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

% Last Modified by GUIDE v2.5 13-May-2005 17:20:09

% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @tls_OpeningFcn, ...
                   'gui_OutputFcn',  @tls_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 tls is made visible.
function tls_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 tls (see VARARGIN)

% Choose default command line output for tls
handles.output = hObject;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Initialize various structure fields to be used later
% Ensure this matches reset values and startup strings
% Uses startup strings defined as part of FIG file
% Done this way to force string formatting to a certain style
% Otherwise could just call pushbutton3 callback
handles.L = 5500; % line length
handles.up = 3e8; % propagation velocity
handles.Z0 = 300; % characteristic impedance--real value for lossless line
handles.Zg = 500 + 0j; % source impedance
handles.ZL = 500 + 0j; % load impedance
handles.f = 1e5; % frequency
handles.Vg = 1; % input voltage (not user selectable)
% Set plotting flag to false
handles.ReadyToPlot = 0;

% Another way to initialize data, but string formatting will be different
%pushbutton3_Callback(hObject, eventdata, handles);

% read and display the diagram of the transmission line setup
handles.diagram = imread('tls.png','PNG'); % Read the image file 
axes(handles.axes1);
image(handles.diagram) % display the image file
axis square; % prevent aspect ratio distortion
set(handles.axes1, 'Visible', 'off'); % turn off the axis labels

% Update handles structure
guidata(hObject, handles);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


% --- Outputs from this function are returned to the command line.
function varargout = tls_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;


% Propagation velocity
function edit3_Callback(hObject, eventdata, handles)
% hObject    handle to edit3 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'String') returns contents of edit3 as text
%        str2double(get(hObject,'String')) returns contents of edit3 as a double
up = str2double(get(hObject, 'String'));
if (isnan(up) || ~isreal(up) || up<=0)  % uses short-circuit logical OR
    set(hObject, 'String', num2str(handles.up));
    errordlg('Propagation velocity must be a real number > 0','Error');
else
    % Save the new value in structure
    handles.up = up;
    handles.ReadyToPlot = 0;
    guidata(hObject,handles)
end

% Propagation velocity
% --- Executes during object creation, after setting all properties.
function edit3_CreateFcn(hObject, eventdata, handles)
% hObject    handle to edit3 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit 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


% Line length
function edit4_Callback(hObject, eventdata, handles)
% hObject    handle to edit4 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'String') returns contents of edit4 as text
%        str2double(get(hObject,'String')) returns contents of edit4 as a double
L = str2double(get(hObject, 'String'));
if (isnan(L) || ~isreal(L) || L<=0)  % uses short-circuit logical OR
    set(hObject, 'String', num2str(handles.L));
    errordlg('Line length must be a real number > 0','Error');
else
    % Save the new value in structure
    handles.L = L;
    handles.ReadyToPlot = 0;
    guidata(hObject,handles)
end

% Line length
% --- Executes during object creation, after setting all properties.
function edit4_CreateFcn(hObject, eventdata, handles)
% hObject    handle to edit4 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit 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


% Characteristic impedance
function edit5_Callback(hObject, eventdata, handles)
% hObject    handle to edit5 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'String') returns contents of edit5 as text
%        str2double(get(hObject,'String')) returns contents of edit5 as a double
Z0 = str2double(get(hObject, 'String'));
if (isnan(Z0) || ~isreal(Z0) || Z0<=0)  % uses short-circuit logical OR
    set(hObject, 'String', num2str(handles.Z0));
    errordlg('Characteristic impedance must be a real number > 0.','Error');
else
    % Save the new value in structure
    handles.Z0 = Z0;
    handles.ReadyToPlot = 0;
    guidata(hObject,handles)
end


% Characteristic impedance
% --- Executes during object creation, after setting all properties.
function edit5_CreateFcn(hObject, eventdata, handles)
% hObject    handle to edit5 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit 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


% Source impedance
function edit6_Callback(hObject, eventdata, handles)
% hObject    handle to edit6 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'String') returns contents of edit6 as text
%        str2double(get(hObject,'String')) returns contents of edit6 as a double
Zg = str2double(get(hObject, 'String'));
if (isnan(Zg) || abs(angle(Zg)) > pi/2)  % uses short-circuit logical OR
    set(hObject, 'String', num2str(handles.Zg));
    errordlg('Source impedance must be a real or complex number (with a positive real component).','Error');
else
    % Save the new value in structure
    handles.Zg = Zg;
    handles.ReadyToPlot = 0;
    guidata(hObject,handles)
end


% Source impedance
% --- Executes during object creation, after setting all properties.
function edit6_CreateFcn(hObject, eventdata, handles)
% hObject    handle to edit6 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit 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


% Load impedance
function edit7_Callback(hObject, eventdata, handles)
% hObject    handle to edit7 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'String') returns contents of edit7 as text
%        str2double(get(hObject,'String')) returns contents of edit7 as a double
ZL = str2double(get(hObject, 'String'));
if (isnan(ZL) || abs(angle(ZL)) > pi/2)  % uses short-circuit logical OR
    set(hObject, 'String', num2str(handles.ZL));
    errordlg('Load impedance must be a real or complex number.','Error');
else
    % Save the new value in structure
    handles.ZL = ZL;
    handles.ReadyToPlot = 0;
    guidata(hObject,handles)
end


% Load impedance
% --- Executes during object creation, after setting all properties.
function edit7_CreateFcn(hObject, eventdata, handles)
% hObject    handle to edit7 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit 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


% Frequency
function edit8_Callback(hObject, eventdata, handles)
% hObject    handle to edit8 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'String') returns contents of edit8 as text
%        str2double(get(hObject,'String')) returns contents of edit8 as a double
f = str2double(get(hObject, 'String'));
if (isnan(f) || ~isreal(f) || f<=0)  % uses short-circuit logical OR
    set(hObject, 'String', num2str(handles.f));
    errordlg('Frequency must be a real number > 0','Error');
else
    % Save the new value in structure
    handles.f = f;
    handles.ReadyToPlot = 0;
    guidata(hObject,handles)
end


% Frequency
% --- Executes during object creation, after setting all properties.
function edit8_CreateFcn(hObject, eventdata, handles)
% hObject    handle to edit8 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit 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


% Calculate output values
% --- 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)

% Select current axes and clear the plot 
axes(handles.axes1);
cla reset;
% display the transmission line diagram
%axes(handles.axes1);
image(handles.diagram) % display the image file
axis square; % prevent aspect ratio distortion
set(handles.axes1, 'Visible', 'off'); % turn off the axis labels


% Extract user data from structure
L=handles.L; % line length
up=handles.up; % propagation velocity
Z0=handles.Z0; % characteristic impedance
Zg=handles.Zg; % source impedance
ZL=handles.ZL; % load impedance
f=handles.f; % frequency
Vg=handles.Vg; % input voltage (not user selectable)

%This code calculates all necessary data for the output and plots
betaL=2*pi*L*f/up;
zoverL=[-1:.01:0];
Zin=Z0*((ZL+j*Z0*tan(betaL))/(Z0+j*ZL*tan(betaL)));
gamma=(ZL-Z0)/(ZL+Z0);
VSWR=(1+abs(gamma))/(1-abs(gamma));
Fact=(Vg*Zin/(Zg+Zin))/(exp(j*betaL)+gamma*exp(-j*betaL));
Vofz=Fact*(exp(-j*betaL*zoverL)+gamma*exp(j*betaL*zoverL));
lambda=up/f;
lim=max(abs(Vofz));
mag=abs(Vofz);
angl=angle(Vofz);
% calculate the animation data
omegat=linspace(0,8*pi,801);
framedata=zeros(801,101);
for i=1:801
    framedata(i,:)=mag.*cos(omegat(1,i)*ones(1,101)+angl);
end

% Write output data to GUI
set(handles.text31, 'String', num2str(gamma)); 
set(handles.text32, 'String', num2str(VSWR));
set(handles.text33, 'String', num2str(Zin));
set(handles.text34, 'String', num2str(lambda));

% Update handles structure
guidata(handles.figure1, handles);

% Store new calculated values in data structure for plots
handles.betaL = betaL; 
handles.zoverL = zoverL; 
handles.Zin = Zin; 
handles.gamma = gamma; 
handles.VSWR = VSWR; 
handles.Vofz = Vofz; 
handles.lambda = lambda; 
handles.mag = mag; 
handles.angl = angl; 
handles.omegat = omegat; 
handles.framedata = framedata;
handles.lim = lim; 
% Set plotting flag to true
handles.ReadyToPlot = 1;

% Update handles structure
guidata(hObject, handles);



% Reset input values
% --- 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)

% Initialize the structure fields
handles.L = 5500; % line length
handles.up = 3e8; % propagation velocity
handles.Z0 = 300; % characteristic impedance
handles.Zg = 500 + 0j; % source impedance
handles.ZL = 500 + 0j; % load impedance
handles.f = 1e5; % frequency
handles.Vg = 1; % input voltage (not user selectable)
% Set plotting flag to false
handles.ReadyToPlot = 0;

% Update handles structure
guidata(hObject, handles);

% write the default input data values to the GUI
% note that source voltage Vg is always 1
% Below are two methods. Using Method 1 the formatting of the strings may not be 
%   what you want.  If you want to control the formatting of the strings
%   explictly, then use Method 2 that follows Method 1
% METHOD 1
% set(handles.edit4, 'String', num2str(handles.L)); %Line length in meters
% set(handles.edit3, 'String', num2str(handles.up)); %Propagation velocity on the line
% set(handles.edit5, 'String', num2str(handles.Z0)); %Line characteristic impedance 
% set(handles.edit6, 'String', num2str(handles.Zg)); %Source impedance 
% set(handles.edit7, 'String', num2str(handles.ZL)); %Load impedance 
% set(handles.edit8, 'String', num2str(handles.f)); %Frequency of driving source in Hz.
%  METHOD 2
set(handles.edit4, 'String', '5500'); %Line length in meters
set(handles.edit3, 'String', '3e8'); %Propagation velocity on the line
set(handles.edit5, 'String', '300'); %Line characteristic impedance 
set(handles.edit6, 'String', '500 + 0j'); %Source impedance 
set(handles.edit7, 'String', '500 + 0j'); %Load impedance 
set(handles.edit8, 'String', '1e5'); %Frequency of driving source in Hz.

% clear the output values
set(handles.text31, 'String', ''); 
set(handles.text32, 'String', ''); 
set(handles.text33, 'String', ''); 
set(handles.text34, 'String', ''); 

% clear the plot axes
axes(handles.axes1);
cla reset;
% display the transmission line diagram
%axes(handles.axes1);
image(handles.diagram) % display the image file
axis square; % prevent aspect ratio distortion
set(handles.axes1, 'Visible', 'off'); % turn off the axis labels

% Update handles structure
guidata(handles.figure1, handles);


% Output: Reflection Coefficient
% --- Executes during object creation, after setting all properties.
function text31_CreateFcn(hObject, eventdata, handles)
% hObject    handle to text31 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit controls usually have a white background on Windows.
%       See ISPC and COMPUTER.


% Output: VSWR
% --- Executes during object creation, after setting all properties.
function text32_CreateFcn(hObject, eventdata, handles)
% hObject    handle to text32 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit controls usually have a white background on Windows.
%       See ISPC and COMPUTER.


% Output: Input Impedance
% --- Executes during object creation, after setting all properties.
function text33_CreateFcn(hObject, eventdata, handles)
% hObject    handle to text33 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit controls usually have a white background on Windows.
%       See ISPC and COMPUTER.


% Output: Wavelength
% --- Executes during object creation, after setting all properties.
function text34_CreateFcn(hObject, eventdata, handles)
% hObject    handle to text34 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit controls usually have a white background on Windows.
%       See ISPC and COMPUTER.


% List of plots; this callback not currently used in this program
% --- 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 = get(hObject,'String') returns popupmenu1 contents as cell array
%        contents{get(hObject,'Value')} returns selected item from popupmenu1

% List of plots 
% --- 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

% Update the plot
% --- Executes on button press in pushbutton4.
function pushbutton4_Callback(hObject, eventdata, handles)
% hObject    handle to pushbutton4 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% make sure Calculate button has been pressed at least once
if (handles.ReadyToPlot == 0)
    myPlotErr=sprintf('Either a new input value was entered\n');
    myPlotErr=sprintf([myPlotErr 'or no outputs have yet been calculated.\n']);
    myPlotErr=sprintf([myPlotErr 'Please press "Calculate Output Data" now.']);
    errordlg(myPlotErr,'New output values required!');
    return;
end

% Select current axes and clear the plot 
axes(handles.axes1);
cla reset;

% Extract values from data structure for plots
betaL=handles.betaL; 
zoverL=handles.zoverL; 
Zin=handles.Zin; 
gamma=handles.gamma; 
VSWR=handles.VSWR; 
Vofz=handles.Vofz; 
lambda=handles.lambda; 
mag=handles.mag; 
angl=handles.angl; 
omegat=handles.omegat; 
framedata=handles.framedata;
lim=handles.lim; 
L=handles.L; % line length
up=handles.up; % propagation velocity
Z0=handles.Z0; % characteristic impedance
Zg=handles.Zg; % source impedance
ZL=handles.ZL; % load impedance
f=handles.f; % frequency
Vg=handles.Vg; % input voltage (not user selectable)


% take action based upon which plot is selected
popup_sel_index = get(handles.popupmenu1, 'Value');
switch popup_sel_index
    case 1
        plot(zoverL,abs(Vofz));
        axis([-1 0 0 1.2*lim])
        xlabel('Dimensionless Distance, z/L')
        ylabel('Standing Wave Amplitude')
    case 2
        omegat2=linspace(0,4*pi,101);
        Vin=Vg*Zin/(Zin+Zg);
        VL=Vin*((1+gamma)/(exp(j*betaL)+gamma*exp(-j*betaL)));
        Vint=abs(Vin)*cos(omegat2+angle(Vin)*ones(1,101));
        VLt=abs(VL)*cos(omegat2+angle(VL)*ones(1,101));
        Vgt=abs(Vg)*cos(omegat2+angle(Vg)*ones(1,101));
        plot([0 omegat2(1,101)], [0 0],'k') % a black line at V=0
        hold on
        %myPlotHandle=plot(omegat2,Vint,'--',omegat2,VLt,'-.',omegat2,Vgt,'.');
        myPlotHandle=plot(omegat2,Vgt,omegat2,Vint,omegat2,VLt);
        hold off
        % in GUI we need explicit handle to axes for legend to work
        legend(myPlotHandle,'v_g','v_i_n','v_L');
        lim2=max(abs([Vg VL Vin]));
        axis([0 4*pi -1.1*lim2 1.1*lim2])
        xlabel('Dimensionless Time, \omega t')
        ylabel('v_g(t), v_i_n(t), v_L(t), volts')
    case 3
        [X,Y]=meshgrid(omegat,zoverL);
        mesh(X,Y,framedata')
        view(45,30)
        text(30, -.6,-1.5*lim,'Distance, z/L','Rotation', 22,'FontSize',12)
        text(3,-1,-1.5*lim,'Dimensionless Time,  \omegat','Rotation',-20,'FontSize',12)
        zlabel('Line Voltage, v(z,t)')
    case 4
        set(handles.pushbutton4,'Enable','Off');  % Gray-out the button
        L=plot(zoverL,framedata(1,:),'k','EraseMode','xor');
        hold on
        plot([-1 -1],[-1.2*lim 1.2*lim])
        hold on
        plot([0 0],[-1.2*lim 1.2*lim])
        hold on
        axis([-1.2 .2 -1.2*lim 1.2*lim])
        xlabel('Dimensionless Distance on the Line, z/L')
        ylabel('Line Voltage, v(z,t)')
        myQuest=sprintf('Click YES to begin the animation.\n');
        myQuest=sprintf([myQuest 'When you wish to stop the animation,\n']);
        myQuest=sprintf([myQuest 'click the grayed-out "Update Plot" button.']);
        ButtonName=questdlg(myQuest,'Animate Plot?','Yes','Cancel','Yes');
        M=plot([-1 0],[framedata(1,1) framedata(1,101)],'o','EraseMode','xor');
        switch ButtonName,
            case 'Cancel',
                set(handles.pushbutton4,'Enable','On');
                return;
            case 'Yes',
                global Animate;
                Animate = 1;
                while (Animate)
                    for i=1:201%801
                        set(L,'Ydata',framedata(i,:))
                        set(M,'Ydata',[framedata(i,1),framedata(i,101)])
                        pause(.01)
                        if (Animate == 0)
                            set(handles.pushbutton4,'Enable','On');
                            return
                        end
                    end
                end

                set(handles.pushbutton4,'Enable','On');
        end % of switch

end % of pushbutton4 Callback


% Executes on mouse press over pushbutton4 when it is grayed-out.
function pushbutton4_ButtonDownFcn(hObject, eventdata, handles)
% hObject    handle to pushbutton4 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

global Animate;
Animate = 0;
 
% for debugging only
%disp('pushbutton4 was pressed!')