uicontrol Handles Error using set

maxDrag = num2str(round(max(data_to_plot)), '%7.5g');

set(handles.maxDrag, 'String', ['Max Drag: ', maxDrag, ' lbs'])

I receive the following error with my use of set. What is wrong with what I have done?

Error using set
Value must be a handle

Error in test>pushbutton_run_Callback (line 188)
   set(handles.maxDrag, 'String', ['Max Drag: ', maxDrag, ' lbs'])

Error in gui_mainfcn (line 96)
        feval(varargin{:});

Error in test (line 60)
    gui_mainfcn(gui_State, varargin{:});

Error in @(hObject,eventdata)test('pushbutton_run_Callback',hObject,eventdata,guidata(hObject))

Error while evaluating uicontrol Callback

Answer 1

[Jan]

The message is clear: handles.maxDrag is not a handle. Then you cannot use it to set properties.

How and where is the field defined? Has the corresponding UI object been deleted already?

Btw.: The error message does not come from the two posted code lines, but from line 188. Perhaps you have edited the M-file but did not save it before running?

[T]

I have edited the second line. I should then write:

maxDrag = handles.maxDrag

[Walter Roberson]

Not likely. your maxDrag is a string created by num2str(). If you overwrite it with a handle then using it as a string will not work. If you overwrite the handle with a string, then using the handle will not work.

Hint: rename the string variable as maxDragstr so that you do not confuse it with maxDrag as a handle.

[T]

It works. I think it's because I didn't take the button using guide.