how can i generate set of point belong to boundary of geometric shape

hi every one,

i want to generate set of point located on the boundary of drawn polygon, can you help me please.

clc;
clear all
Xmin=0; Xmax=5; Ymin=0; Ymax=5;
hold on; grid on;
axis([Xmin Xmax Ymin Ymax]);

xx=[1 1 3.8 3.8 3 3 1];
yy=[3 3.7 3.7 1 1 3 3];
plot(xx,yy);
hold on

xxxx=[1 1 4.5 4.5 4 4 1];
yyyy=[4 4.5 4.5 1 1 4 4];
plot(xxxx,yyyy);