>> help figure
FIGURE Create figure window.
FIGURE, by itself, creates a new figure window, and returns
its handle.
FIGURE(H) makes H the current figure, forces it to become visible,
and raises it above all other figures on the screen. If Figure H
does not exist, and H is an integer, a new figure is created with
handle H.
So, if you want to always plot on the same figure, you can use h=figure(1), which may not be good in some cases because it over-write the existing figure 1.
Or, you can use close() to close the existing figure first.
In any case, remember figure has a handle. It is like the figure's ID. You can always specify to which figure you want to plot.
h1=figure(1);
set(h1,'name','myname');
plot(1:10);
