Error after clicking in pushbutton "Parent must be a scalar graphics handle."

% --- 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)


%%Jesli radio1 jest zaznaczone to obliczy deformacje pomiaru 0-N
%%Obliczanie Obniżeń
[num,txt]=xlsread('dane0.xlsx');
num(isnan(num))=00;
x=num


set(handles.tabela0,'data',x);

x=get(handles.tabela0,'data');
w=x(:,3)-x(:,2);
wpoz=x(1:end,1);
calosc=[wpoz w]

set(handles.tabelaw,'data',calosc);
x=get(handles.tabela0,'data');

wykresww = findobj('Tag', 'axes1');
plot(wykresww,calosc(1:2:end,1),calosc(1:2:end,2));

After clicking Run, and click in pushbutton2 I have results but If I click again in pushbutton2 I have error:

Answer 1

[Adam Danz]

Whenever you're troubleshooting an error in this forum, include the entire error message and indicate what line is causing the error. I have a pretty good guess at the source of the error but I'm not certain without having that information.

Possible source

I think the first line below returns an empty value in wykresww or it returns more than one handle.

wykresww = findobj('Tag', 'axes1');
plot(wykresww,calosc(1:2:end,1),calosc(1:2:end,2));

If it's empty, that means you don't have an object with the tag 'axes1'. If it has more than one handle, that means you have multiple objects with the tag 'axes1'.

Solution

Rather than searching for your axis, why not grab its handle directly from the 'handles' variable? For example, if the handle to your axis is handles.axis1,

plot(handles.axis1, calosc(1:2:end,1), calosc(1:2:end,2));

If you must use findobj() (which you shouldn't) you need to make sure it's finding the correct object.

[Steven Lord]

In this case, that findobj call is finding at least three axes (the three on the bottom row of the app window.) Only the left-most of those axes appears to have something in it. Graphics objects may have at most one Parent, and the plot call is trying to make a line with at least 3.

[Adam Danz]

findobj() will identify those axes only if they have the tag "axes1" which might be the case. The same error would occur if findobj() returns an empty output after finding no objects with the tag "axes1".

[Steven Lord]

You are correct. I read too quickly and assumed the findobj call was looking for 'Type', 'axes'.

Given that, you're right that it's probably empty. Calling plot (as MATLAB did the first time it ran the callback, when the user pressed the button the first time) cleared the Tag property.