Hey Guido,
I understand that you want to know what are the benefits of UserData over guidata.
UserData is a property that all graphics objects in MATLAB possess, and can be used to store any single, user-defined array with a particular object. While you cannot access an application data unless you know its name, any user-defined data (if it exists) can always be accessed using 'UserData' property with SET and GET methods.
h = surf(peaks);
set(h,'UserData',rand(5));
ud = get(h,'UserData');
GUIDATA is a function used to associate data with the figure containing the GUI. GUIDATA can manage only one variable at a time and hence the variable is usually defined to be a structure with mutliple fields. GUIDATA is commonly used to share handles to different sub-components of the GUI between the various callbacks in the GUI. GUIDE uses GUIDATA similarly to store and maintain the handles structure.
Internally, GUIDATA actually uses a particular entry in the application data to store the information. This can be seen by viewing the contents of GUIDATA:
edit guidata
---------------------------guidata.m----------------------------
% choose a unique name for our application data property.
% This file should be the only place using it.
PROP_NAME = 'UsedByGUIData_m';
% ...SNIP...
if nargin == 1 % GET
data = getappdata(fig, PROP_NAME);
else % (nargin == 2) SET
setappdata(fig, PROP_NAME, data_in);
end
In general, GUIDATA should be used to store and access information from the 'handles' structure, especially in GUIDE-generated GUIs. Saving large amounts of data in the 'handles' structure can sometimes cause a considerable slowdown, especially if GUIDATA is often called within the various sub-functions of the GUI.
I hope this helps!
