MATLAB Answers


how to switch YLim from auto to manual using contextmenu

Asked by G A
on 19 Jan 2013

The following code works OK, switching y limit in Fig3_axes.

    ylim_menu = uicontextmenu;
    hcb1 = 'set(gco, ''YLimMode'',''auto'')';
    hcb2 = 'set(gco, ''Ylim'',[0,1])';
    uimenu(ylim_menu, 'Label', 'auto', 'Callback', hcb1);
    uimenu(ylim_menu, 'Label', 'manual', 'Callback', hcb2);

However, when I try to replace [0,1] by a variable

 hcb2 = 'set(gco, ''Ylim'',Fig3yLim)';

I am getting an error:

Undefined function or variable 'Fig3yLim'.
Error while evaluating uimenu Callback

How can I use the variable?



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1 Answer

Answer by Jan Simon
on 19 Jan 2013
Edited by Jan Simon
on 19 Jan 2013
 Accepted answer

Yes, of course. Callbacks are evaluated in the base workspace. If you use a variable, which is defined in a function, it is not known when the callback runs.

Better use function for callbacks and store variables in the figure by guidata.

uimenu(ylim_menu, 'Label', 'auto',   'Callback', {@uimenu_Callback, 'auto'});
uimenu(ylim_menu, 'Label', 'manual', 'Callback', {@uimenu_Callback, '01'});
function uimenu_Callback(uimenuH, EventData, Command)
handles = guidata(uimenuH);
switch Command
  case '01'
    set(handles.Fig3_axes, 'YLim', [0, 1]);
  case 'auto'
    set(handles.Fig3_axes, 'YLimMode', 'auto');
    error('Unknown command - programming error');

Now the contents of the variable Fig3yLim can by added as 4th input argument.

Defining callbacks as strings is supported for backward compatibility with Matlab 5.3 (1999). Using function handles is more secure and efficient.

  1 Comment

on 19 Jan 2013

Thanks Jan, it works now.

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