You can store the handles of objects you want to delete later:
AxesH = axes('NextPlot', 'add');
LineH = plot(1:10, rand(1, 10));
set(AxesH, 'UserData', LineH);
...
pause(2);
OldLineH = get(AxesH, 'UserData');
delete(OldLineH);
LineH = plot(1:10, rand(1, 10));
Setting 'NextPlot' to 'add' is equivalent to "hold on". Setting it to 'replace' let the plot() command remove all previously plotted objects automatically.
