The cause of 'Error while evaluating uicontrol Callback' in GUI window

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Aaron Smith 2017-5-24

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评论： Jan 2020-12-18

new_window_2.m

I have encountered this error in running a GUI window that I have created. From what I have been able to discern online, it is caused by a problem with the handle structure but the piece of code that continues to be identified by matlab as the problem is this:

Error in new_window_2>pushbutton1_Callback (line 190)
set(handles.verticalBin, 'enable', 'on');

I have changed a number of lines in the code but i am not sure how this (or other set(handles, 'enable', '') statements) are causing an error. How might the handles structure be failing to work properly to generate this error?

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Jan 2017-5-24

The handle struct is not the problem. Please post the complete error message. Currently we see only the part, which defines where the problem is, but not what.

Stephen23 2017-5-25

Good code does not use globals: "I have never seen MATLAB code where globals were the right thing to do.... Most of the time I have seen globals being used it was a situation where the code author did not understand scoping of variables. Rather than pass variables from one function to another, they were just being made global."

http://blogs.mathworks.com/videos/2010/03/08/top-10-matlab-code-practices-that-make-me-cry/

Note that using globals is a programming practice that will make your code very hard to debug. Passing arguments is much more robust, and is the recommended way of passing data between workspaces:

http://www.mathworks.com/help/matlab/matlab_prog/share-data-between-workspaces.html

https://www.mathworks.com/matlabcentral/answers/14857-where-do-people-learn-bad-programming-habits-i-e-goto-global-and-eval

https://www.mathworks.com/matlabcentral/answers/51946-systematic-do-not-use-global-don-t-use-eval

https://www.mathworks.com/matlabcentral/answers/74626-how-to-declear-global-array-and-how-to-use-it

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Answer 1

Jan 2017-5-24

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Using globals is a really bad idea. This impedes the debugging, because you cannot find reliable, which code is resposnible for the last change. Do not use such an indirect method, but the handles struct, which is used for sharing other details already.

It is not clear, where the object of the handle handles.verticalBin is created. Are you sure that this field is existing in the handles struct?

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Aaron Smith 2017-5-26

编辑：Aaron Smith 2017-5-26

在 MATLAB Online 中打开

I replaced the globals with handles in a way i think should work but there is an error with the equals signs (=) i used.

Essentially, i gave the handles.option handle a different value in each of my pushbutton callbacks (1, 2 & 3) and then in the callback for for the radio buttons i replaced the globals in the if statement with:

 if  handles.option = 1                     % If this button is pushed, Bin the corresponding file
    handles = guidata(hObject);
    binnedH = sum(handles.finishCellfull, 2);
    handles.horizontalBin = stairs(binnedH);
    guidata(hObject, handles);
elseif handles.option = 2               % If this button is pushed, Bin the corresponding file
    handles = guidata(hObject);
    binnedH = sum(handles.finishCellhalf, 2);
    handles.horizontalBin = stairs(binnedH);
    guidata(hObject, handles);
else                                         % If this button is pushed, Bin the corresponding file
    handles = guidata(hObject);
    binnedH = sum(handles.finishCellquarter, 2);
    handles.horizontalBin = stairs(binnedH);
    guidata(hObject, handles);
end

The error is with the equals in handles.option = 1; and handles.option = 2;

Aaron Smith 2017-5-26

在 MATLAB Online 中打开

Thanks Adam, I thought the == meant that the value is exactly equal to 1 and the = was a more rough equality.

This has fixed that error but the error with verticalBin still remains.

Reference to non-existent field 'verticalBin'.
Error in new_window_2>pushbutton4_Callback (line 249)
set(handles.verticalBin, 'enable', 'on');
Error in gui_mainfcn (line 96)
        feval(varargin{:});
Error in new_window_2 (line 42)
    gui_mainfcn(gui_State, varargin{:});
Error in @(hObject,eventdata)new_window_2('pushbutton4_Callback',hObject,eventdata,guidata(hObject))
Error while evaluating uicontrol Callback

I'm not sure why verticalBin causes an error while horizontalBin does not when the callbacks are essentially the same. Unless verticalBin is just the first encountered by the code and horizontalBin will also cause an error. If so, I'm still not sure what the error is caused by. The callback simply sums the data and then plots it like the other, pushbutton callbacks. Might this error disappear if I were to move the callbacks for the radio buttons after the callbacks for the pushbutton in the code?

Aaron Smith 2017-5-26

I was from when I first started off learning basic calculations using notation such as ==, =>, etc. I may have carried it over from here or simply misunderstood the operators when beginning

Adam 2017-5-30

在 MATLAB Online 中打开

It can be difficult with some of these operators because as a beginner (sometimes as a more experienced user too) it can be hard to know what to type in the help to get to the right documentation page. Searching for just '=' or '==' does not yield anything so it is useful to know the function name equivalents to search e.g.

doc eq

The assignment operator is a tricky one though, I'm not aware it has a function-based equivalent given its nature and I must admit I gave up trying to work out where in the help it is introduced and defined. I'm sure it is somewhere linked from the Matlab introductory pages, but I didn't find it. Thankfully I know how it works so I don't need to find it on this occasion!

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Answer 2

mohammadreza mahmoudi 2020-12-18

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编辑：mohammadreza mahmoudi 2020-12-18

hi dear friends and professors.

how can i solve this problem?

Error: label vector and instance matrix must be double

Unable to perform assignment because the indices on the left side are not compatible with the size of the rightn side.

Error in main>multisvm (line 991)

models(k) = svmtrain(TrainingSet,G1vAll);

Error in main>pushbutton14_Callback (line 866)

result = multisvm(data_feat,data_label,test_data);

Error in gui_mainfcn (line 95)

feval(varargin{:});

Error in main (line 18)

gui_mainfcn(gui_State, varargin{:});

Errorin matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)main('pushbutton14_Callback',hObject,eventdata,guidata(hObject))

Error while evaluating UIControl Callback.

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Jan 2020-12-18

Please open a new thread to ask a new question. This is the section for answers to another question.

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