Index exceed matrix dimensions in GUI

Hye i have problem with this error, here is my code in pushbutton1_callback:

 global r;                
[a, b]=uigetfile('.bmp');
img=imread([b a]);
imshow(img,'Parent',handles.axes1);
if  (a =='1.bmp')
    d = r(1,:);
elseif (a =='2.bmp')
    d = r(5,:);
elseif (a =='3.bmp')
    d = r(9,:);
  end

and the error is:

--> Index exceeds matrix dimensions.
-->Error in SystemDemo1>pushbutton1_Callback (line 86)
  d = r(1,:);
--> Error in gui_mainfcn (line 95)
      feval(varargin{:});
-->Error in SystemDemo1 (line 42)
  gui_mainfcn(gui_State, varargin{:});
-->Error in matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)SystemDemo1('pushbutton1_Callback',hObject,eventdata,guidata(hObject)) 
Error while evaluating UIControl Callback

and r is actually a variable in matlab workspace. but i want the contents in r which the value is in double to be used in my gui. So, thats why im using global. Hope any of you guys could help me as im new in using function in GUI and it seems complicated/hard for me because im never used it. Any advice or help will be really appreciated. Thank you so much.

[Rik]

Did you set the variable in your normal workspace as a global as well?

Also, try to find an alternative to your use of a global (like setappdata (and getappdata), or changing the way your function starts so you can supply it as an input and get it saved with guidata), or make the name of that global very descriptive and let it contain the name of the function. If you do that, you are not likely to have your variable collide with another global from another piece of code.

[Nurul Atifah]

May you provide with sample of code how should i do it? so i can get better view on how i could fix it? the variable in the normal workspace not yet set to global? how i should do it.

[Jan]

Do not compare char vectors by the elementwise comparison ==, but by strcmp:

% if a =='1.bmp'  replace by:
if strcmp(a, '1.bmp')

[Dennis]

There are a quite a few alternatives to global variables. If you want to use globals you need to declare said global in every function/script you are using.

For further information about passing data between callbacks please have a look here: https://de.mathworks.com/help/matlab/creating_guis/share-data-among-callbacks.html

In your case i suggest to either pass r as additional input to your function

function pushbutton1_callback(hObject,~,r)

and when you create your pushbutton:

Callback,{@pushbutton1_callback,r}

or use setappdata/getappdata like Rik Wiselink suggests:

After you created your pushbutton:

setappdata(handles.pushbutton1,'r',r);

In your function:

r=getappdata(hObject,'r');

I do not know if hObject and handles.pushbutton1 are correct in your case since those parts of your code are missing.

[Nurul Atifah]

my function is

function pushbutton1_Callback(hObject, eventdata , handles)

as this the one that comes out when i want to edit my callback function.

Answer 1

[Ameer Hamza]

Have you declared r as global in command window by running

global r

You need to run global r both in the command window and your app code. Another way is to use evalin() to get value from base workspace directly in GUI without using global. Use it like this

r = evalin('base', 'r');

Note that all of these options are unrecommended. See Here: https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval. You should consider @Rik's suggestion to improve the reliability of your code.

[Nurul Atifah]

okay i already tried what both of you had suggest. luckily, its no error while i browse the picture. but then i can not display the picture at axes1 that i declare. the error is:

-->Not enough input arguments.
-->Error in SystemDemo1>pushbutton1_Callback (line 84)
imshow(img,'Parent',handles.axes1);
-->Error in gui_mainfcn (line 95)
      feval(varargin{:});
-->Error in SystemDemo1 (line 42)
  gui_mainfcn(gui_State, varargin{:});
-->Error in
matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)SystemDemo1('pushbutton1_Callback',hObject,eventdata,guidata(hObject)) 
-->Error while evaluating UIControl Callback

i had change '=' to strcmp and i used function and callback that u had suggest. Just the picture is not showing at the axes/box that i had created.

[Dennis]

Try this:

function pushbutton1_Callback(hObject, ~ , ~)
  r=getappdata(hObject,'r');
  [a, b]=uigetfile('.bmp');
  img=imread([b a]);
  imshow(img,'Parent',handles.axes1);
  if  strcmp(a,'1.bmp')==1
      d = r(1,:);
  elseif strcmp(a,'2.bmp')==1
      d = r(5,:);
  elseif strcmp(a,'3.bmp')==1
      d = r(9,:);
  end

In your other script/function you should have two lines like this:

handles.pushbutton1=uicontrol('Style','pushbutton','String','My Pushbutton','Callback',{@pushbutton1_Callback}); %add/edit string/position/parent...if needed 
setappdata(handles.pushbutton1,'r',r)

[Nurul Atifah]

Is it true if i wrote like this:

function pushbutton1_Callback(hObject,~ , ~)
% 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)
global r;
r=getappdata(hObject,'r');
[a, b]=uigetfile('.bmp');
img = imread([b a]);
imshow(img,'Parent',handles.axes1);
if  strcmp(a,'1.bmp')==1
  d = r(1,:);
elseif strcmp(a,'2.bmp')==1
  d = r(5,:);
elseif strcmp(a,'3.bmp')==1
  d = r(9,:);
end
handles.pushbutton1=uicontrol('Style','pushbutton','String','My Pushbutton','Callback',{@pushbutton1_Callback}); 
setappdata(handles.pushbutton1,'r',r)

if i wrote like this, and when i run my code it got error which is:

-->Undefined function or variable 'handles'.

-->Error in SystemDemo1>pushbutton1_Callback (line 86) imshow(img,'Parent',handles.axes1);

-->Error in gui_mainfcn (line 95) feval(varargin{:});

-->Error in SystemDemo1 (line 42) gui_mainfcn(gui_State, varargin{:});

-->Error in matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)SystemDemo1('pushbutton1_Callback',hObject,eventdata,guidata(hObject)) Error while evaluating UIControl Callback

and before i run my gui, i loaded my trained data into the workspace which is in form of .mat. And variable 'r' is actually from the .mat file. So, i want to access the value in r if possible.

[Dennis]

You have only shared your callback function. The setappdata and uicontrol lines need to go in your gui/guide script or function where you create your button.

Do you need to load your data into base workspace or can you load it inside your gui? You could aswell pass r as function input when you call your gui.

[Rik]

Why don't you load the mat file when you start the GUI in the openingFcn?

[Nurul Atifah]

may i know how should i load it in the openingFcn. Is it by using evalin ('base', 'filename.mat')? or there is another way to load my .mat in the workspace so i could use it during operating my GUI. @Rik

[Dennis]

my_data = load('filename.mat','-mat'); %returns a structure

[Nurul Atifah]

@Dennis, Is it i should write this line

handles.pushbutton1=uicontrol('Style','pushbutton','String','My Pushbutton','Callback',{@pushbutton1_Callback}); %add/edit string/position/parent...if needed 
setappdata(handles.pushbutton1,'r',r)

under function pushbutton1_KeyPressFcn(hObject, eventdata, handles) or function pushbutton1_KeyReleaseFcn(hObject, eventdata, handles)

im sorry if im troubling you guys but it is because im really new to this.

[Nurul Atifah]

I had try to load it but it doesn't show up at the workspace but the system can be run, and here is how i write it back:

% --- Executes just before SystemDemo1 is made visible.
function SystemDemo1_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 SystemDemo1 (see VARARGIN)
load('TrainedData.mat','-mat');
% Choose default command line output for SystemDemo1
handles.output = hObject;
% Update handles structure
guidata(hObject, handles);

[Stephen23]

@Nurul Atifah: Using a GUI to magically "poof" data into the base workspace and then perform operations on it only causes problems, and makes code complex and buggy. You should simply load the data into some function workspace within the GUI (e.g. a callback) and the pass it around the GUI using the methods explained to you (e.g. guidata). Forget about the base workspace. Learn to love function workspaces.

"there is another way to load my .mat in the workspace so i could use it during operating my GUI"

You don't need to spam that data into the base workspace (and it would be bad code that does that). What you load it is already in one of the GUI function workspaces, so you can simply work with it directly inside the GUI.

You should not magically make variables appear in other workspaces using global, evalin or assignin, unless you want to force yourself into writing slow, complex, buggy code that is hard to debug.

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

[Nurul Atifah]

1. did you mean i should create another button where it state 'load data' and later under the function for the button, i wrote the load('TrainedData.mat','-mat');?

2. And do you mean that .mat file will not appear at the workspace but it actually can be used for entire GUI?

3. Later, how my image could be link with the variable in .mat file if there is no appearance of the .mat file in the workspace?

4. Do i need to use global so that my data can be access entirely in my GUI?

[Dennis]

my bad, you wont need

handles.pushbutton1=uicontrol('Style','pushbutton','String','My Pushbutton','Callback',{@pushbutton1_Callback}); %add/edit string/position/parent...if needed

that line actually creates a button, i falsely assumed guide would include these lines.

Just add

my_data = load('filename.mat','-mat'); %returns a structure
if isfield(my_data,'r')==1   %checks if r exists in my_data
    r=my_data.r;      %gets r from structure 
    setappdata(handles.pushbutton1,'r',r)   %stores r, 
end

to your OpeningFcn

If you need more than only r you can pass the entire structure with setappdata.

1.) You could create a button to load data, but if you need to load data only once it wont be necessary

2.)yes, you wont see any variables in your base workspace, but as long as you pass them around your gui properly you can use them.

3.) the variables are actually in the function workspace

4.) no please do not use globals :)

[Stephen23]

1. I have no idea what that means. However it is your GUI design, so you can load data whenever you want.
2. There is not such thing as " the workspace". The base workspace is just one of them, every function has its own workspace. Your GUI is full of functions, ergo it is full of workspaces that you can load data into (and pass data between). Read more here: https://www.mathworks.com/help/matlab/matlab_prog/base-and-function-workspaces.html
3. Again, there is no such thing as " the workspace". When you load your data into the workspace of a function then that is where the data is. You do not need to magically "poof" everything into the base workspace (unless you want to write spaghetti code).
4. Do not use global variables. As the others have already written, use guidata, or nested functions, or setappdata & getappdata.

https://www.mathworks.com/help/matlab/creating_guis/share-data-among-callbacks.html

[Nurul Atifah]

ohh i see. so the variables is in the function workspace. is it possible if i can view the function workspace cause it makes it more easy to know whether im doing it wrong or not.

and if i want not only r , so did i just add the variables in the code that you show to me? eg:

if isfield(my_data,'r')==1   %checks if r exists in my_data
  r=my_data.r;      %gets r from structure
  setappdata(handles.pushbutton1,'p',p)   
elseif isfield (my_data,'p') ==1
  p = my_data.p
  setappdata(handles.pushbutton1,'p',p)  
end

and i still got this error where my pic wont display

-->Undefined variable "handles" or class "handles.axes1".
-->Error in SystemDemo1>pushbutton1_Callback (line 92)
imshow(img,'Parent',handles.axes1);
-->Error in gui_mainfcn (line 95)
      feval(varargin{:});
-->Error in SystemDemo1 (line 42)
  gui_mainfcn(gui_State, varargin{:});
-->Error in
matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)SystemDemo1('pushbutton1_Callback',hObject,eventdata,guidata(hObject)) 
-->Error while evaluating UIControl Callback

[Dennis]

Yes, you can pass other variables or even the entire struct.

setappdata(handles.pushbutton1,'my_data',my_data)

In the code you have shown you are passing p twice and dont pass r

Does your callback function start like this:

   function pushbutton1_Callback(hObject,eventdata,handles)