how can I add label to rectangle object ?

I did not go through the 'draggable' function, but I assume it allows you to interactively drag the square. I believe the following code should do the same:

pos = [1 2 5 6];
rect = rectangle('Position',pos);
set(rect,'FaceColor','none','EdgeColor','g','LineWidth',6);
axis([0 10 0 10])
rect_title(rect,'title')

Just define the following function first:

function rect_title(rect,str)
global updateflag
updateflag = false;
% Add initial title to UserData
rect.UserData.str = str;
rect.UserData.t = text(rect.Position(1)+rect.Position(3)/2,rect.Position(2)+rect.Position(4)/2,rect.UserData.str,'HorizontalAlignment','center');
% Add Callbacks
ax = rect.Parent;
f = ax.Parent;
f.WindowButtonUpFcn = @draw_rectangle;
rect.ButtonDownFcn = @draw_rectangle;
end
function draw_rectangle(src,evt)
global updateflag
if ishandle(src) && strcmp(get(src,'type'),'figure') && updateflag
    % Assign temporary data to rect
    RectData = src.UserData.RectData;
    % Move Rectangle
    Pold = RectData.rect.Position;
    P1 = RectData.Pdown.IntersectionPoint;
    P2 = evt.IntersectionPoint;
    dx = P2(1) - P1(1);
    dy = P2(2) - P1(2);
    RectData.rect.Position = Pold + [dx dy 0 0];
    % Update title
    delete(RectData.t)
    RectData.rect.UserData.t = text(RectData.rect.Position(1)+RectData.rect.Position(3)/2,RectData.rect.Position(2)+RectData.rect.Position(4)/2,RectData.rect.UserData.str,'HorizontalAlignment','center');
    updateflag = false;
elseif ishandle(src) && strcmp(get(src,'type'),'rectangle')
    updateflag = true;
    ax = src.Parent;
    f = ax.Parent;
    f.UserData.RectData.t = src.UserData.t;
    f.UserData.RectData.rect = src;
    f.UserData.RectData.Pdown = evt;
end
end