MATLAB: Errors in spring mass gui code

Question

Hello,

I am creating a spring mass GUI for my final project in MATLAB. It runs most of the time, but sometimes it gives me an error.

When I input:

position at time=0: 2

velocity at time=0: 1

mass: 2

Damping coefficient: 500

Spring constant: 16000

External Force: 3400

I get an error stating:

Array indices must be positive integers or logical values.

Error in SpringMassP>pushbutton1_Callback (line 220)

P=circular(y(k)+1,.5,.5,'r')

Error in gui_mainfcn (line 95)

feval(varargin{:});

Error in SpringMassP (line 44)

gui_mainfcn(gui_State, varargin{:});

Error in

matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)SpringMassP('pushbutton1_Callback',hObject,eventdata,guidata(hObject))

Error while evaluating UIControl Callback.

I am wondering if someone can tell me why? It seems like when I keep my damping coefficient under 200 i dont get errors. Heres the code and .fig attached.

function varargout = SpringMassP(varargin)


% SPRINGMASSP MATLAB code for SpringMassP.fig
%      SPRINGMASSP, by itself, creates a new SPRINGMASSP or raises the existing
%      singleton*.
%


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

% Last Modified by GUIDE v2.5 19-May-2019 07:20:20

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

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

% Update handles structure
guidata(hObject, handles);

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


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



function mass_Callback(hObject, eventdata, handles)
% hObject    handle to mass (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 mass as text
%        str2double(get(hObject,'String')) returns contents of mass as a double


% --- Executes during object creation, after setting all properties.


function mass_CreateFcn(hObject, eventdata, handles)
% hObject    handle to mass (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



function sprconst_Callback(hObject, eventdata, handles)
% hObject    handle to sprconst (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 sprconst as text
%        str2double(get(hObject,'String')) returns contents of sprconst as a double


% --- Executes during object creation, after setting all properties.
function sprconst_CreateFcn(hObject, eventdata, handles)
% hObject    handle to sprconst (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



function damp_Callback(hObject, eventdata, handles)
% hObject    handle to damp (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 damp as text
%        str2double(get(hObject,'String')) returns contents of damp as a double


% --- Executes during object creation, after setting all properties.
function damp_CreateFcn(hObject, eventdata, handles)
% hObject    handle to damp (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



function fext_Callback(hObject, eventdata, handles)
% hObject    handle to fext (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 fext as text
%        str2double(get(hObject,'String')) returns contents of fext as a double


% --- Executes during object creation, after setting all properties.
function fext_CreateFcn(hObject, eventdata, handles)
% hObject    handle to fext (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


% --- 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)

%Below section deals with all the inputs from the user, graphs the
%results, and displays the equation.

syms x m u k f x(t)
f=str2sym(get(handles.fext,'String'))%Converting the input vars to symbolic
m=str2sym(get(handles.mass,'String'))
u=str2sym(get(handles.damp,'String'))
k=str2sym(get(handles.sprconst,'String'))
Dx=diff(x) %Defines Dx to be the first derivative of x
D2x=diff(x,2) %Defines D2x to be the second derivative of x
ode=m*D2x+u*Dx+k*x==f %Defining my differential spring mass equation to be "ode"
ICx=str2num(get(handles.initialposition,'String')) %Allowing user to enter initial conditions
ICv=str2num(get(handles.initialvelocity,'String'))
a=dsolve(ode,x(0)==ICx, Dx(0)==ICv)
set(handles.answer,'String',char(a));
axes(handles.axes2)
[time,position]=fplot(a,[0 5]);
%I want the below loop to run while the other graph is being drawn on
%handles.animation. Not quite sure how to do this..
%Somehow I need to get the below loop to plot what it is trying to plot in
%tandem with the plot for handles.animation starting on line 214
%for i=1:length(time)
 %   plot(time(i),position(i),'x')
  %  hold on
   % plot(time(1:k),position(1:k))
    %pause(.001)
%end
plot(time,position)
fplot(a,[0 5]); %one output will be the x axis and one will be the y. once we specify the function it will
Q=time; %This is the time array of the function graphed
V=position %This is the position array of the function graphed
%G=V(end);
%x0=sum(logical(diff(sign(V)))); %This obtains the number of times the
%graph crosses the origin, but i dont need that

axes(handles.Animation)
%A1=V(1); %I dont need these two
%B1=length(V);
y=V; %V is the position array of the graph that is graphed in axes2

for k=V(1):5:length(V)-1 %My loop is going from the first entry of V array, to the last entry,
   hold on
   A3=mean(V);
   J=round(A3)
   P=circular(y(k)+1,.5,.5,'r')
  xleft=min(V);
  % xright=max(V);
  % axis([xleft xright -2 4]) 
   X=[xleft-1,xleft+1,xleft+1+((V(k)-xleft)/9),xleft+1+2*((V(k)-xleft)/9),xleft+1+3*((V(k)-xleft)/9),xleft+1+4*((V(k)-xleft)/9),xleft+1+5*((V(k)-xleft)/9),1+y(k)]
   Y=[.5,.5,1,0,1,0,1,.5] 
   plot(Y,X,'b','linewidth',1) %I changed these to plot y,x so we can have a vertical graph
   set(gca,'Ydir','reverse')
   pause(.2)
   P=circular(y(k)+1,.5,.5,'w-')
   plot(Y,X,'w','linewidth',1)
   %set(gca,'Ydir','reverse')
end
   
   
   
guidata(hObject,handles);

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


% --- Executes on button press in checkbox1.
function checkbox1_Callback(hObject, eventdata, handles)
% hObject    handle to checkbox1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hint: get(hObject,'Value') returns toggle state of checkbox1
checkboxValue = get(handles.checkbox1, 'value')
if checkboxValue
  set(handles.text19, 'Visible', 'on');
else
  set(handles.text19, 'Visible', 'off');
end


% --- Executes on selection change in popupmenu2.
function popupmenu2_Callback(hObject, eventdata, handles)
% hObject    handle to popupmenu2 (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 popupmenu2 contents as cell array
%        contents{get(hObject,'Value')} returns selected item from popupmenu2


% --- Executes during object creation, after setting all properties.
function popupmenu2_CreateFcn(hObject, eventdata, handles)
% hObject    handle to popupmenu2 (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



function initialposition_Callback(hObject, eventdata, handles)
% hObject    handle to initialposition (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 initialposition as text
%        str2double(get(hObject,'String')) returns contents of initialposition as a double


% --- Executes during object creation, after setting all properties.
function initialposition_CreateFcn(hObject, eventdata, handles)
% hObject    handle to initialposition (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



function initialvelocity_Callback(hObject, eventdata, handles)
% hObject    handle to initialvelocity (see GCBO)


% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)


            
            

    

        

	
    

        
Best Answer
    

    

								

								
William - the code around the error is
y=V; %V is the position array of the graph that is graphed in axes2
for k=V(1):5:length(V)-1 %My loop is going from the first entry of V array, to the last entry,
   hold on
   A3=mean(V);
   J=round(A3)
   P=circular(y(k)+1,.5,.5,'r')
   % etc.
As your comment states, V is the position array. The code then iterates from V(1) to the one less than the length of V with a step size of 5. This may be fine for some cases, but what happens when V(1) is not an integer. Then k is not an integer, and you are using a non-integer index into y at
   P=circular(y(k)+1,.5,.5,'r')
So do you really want to initialize k to be V(1) to be used as an index, or would you rather just have
   for k=1:5:length(V)-1 %
and so be guaranteed an integer on each iteration of the loop?
						    
						
		
    
        

    

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In your callback for edit1 you replace the handle with the value extracted from the handle. That is confusing at the very least.
						    
						
MATLAB: Trouble in code with error “index exceeds number of elements”

								

								
Hi,
In your code, k=1:length(y) has to be k=1:length(y)-1. Because you are trying to access y(k+1) when you have the length of y up to k.
Good luck.
						    
						
        
        

            
            
            
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Answer 1

William - the code around the error is

y=V; %V is the position array of the graph that is graphed in axes2
for k=V(1):5:length(V)-1 %My loop is going from the first entry of V array, to the last entry,
   hold on
   A3=mean(V);
   J=round(A3)
   P=circular(y(k)+1,.5,.5,'r')
   % etc.

As your comment states, V is the position array. The code then iterates from V(1) to the one less than the length of V with a step size of 5. This may be fine for some cases, but what happens when V(1) is not an integer. Then k is not an integer, and you are using a non-integer index into y at

   P=circular(y(k)+1,.5,.5,'r')

So do you really want to initialize k to be V(1) to be used as an index, or would you rather just have

   for k=1:5:length(V)-1 %

and so be guaranteed an integer on each iteration of the loop?