Erasing freehandrois in a stack shared via handles

I want to be able to erase a collection of freehandrois that I've drawn on an image successively. I decided to use a stack-like vector that adds and erases its last elements. I declared it in OpeningFcn and shared it via handles using

handles.freehandrois =[];

I use a radiobutton to draw with imfreehand while its active and a pushbuton to order the erasing of the last freehandroi.

It isn't working, I'm getting the following error:

Subscript indices must either be real positive integers or logicals.

Error in PROTO_TESIS1>pushbutton6_Callback (line 333)
delete(handles.freehandrois(end));

What's wrong with this code?

function radiobutton1_Callback(hObject, eventdata, handles)
while(get (hObject, 'Value')) %while the radiobutton 'Draw Segmentation Seeds' is active 
  freehandroi=imfreehand('Closed', false) 
  handles.freehandrois= [handles.freehandrois;freehandroi]; %%add the new roi to the shared structure  
end
guidata(hObject, handles);

function pushbutton6_Callback(hObject, eventdata, handles)

delete(handles.freehandrois(end));
guidata (hObject, handles);

Answer 1

[Image Analyst]

freehandrois is a field of a structure. handles is a structure. To totally get rid of it you need to use

rmfield(handles, 'freehandrois');

But imfreehand returns a handle, not a list of x,y coordinates so you don't want to simply append the handle to an existing list like that because there would be no way to tell where one stops and the other begins and you keep overwriting the handle. You'd want to store the mask into a cell array, something like

handles.freehandrois(end+1) = {freehandroi.createMask};

then to delete the last one

handles.freehandrois(end) = [];