You can draw circles in MATLAB using the rectangle command and setting the Curvature to [1 1]. (I know, it is a little strange to use the rectangle command to draw circles).
For example, to draw a circle at center [2 3] with a radius of 1.5, you could use the following code.
(Note, you can condense this all down to one line of code, but I've written it using several variables so you can see where all the numbers are coming from.)
center = [2 3];
radius = 1.5;
x = center(1) - radius;
y = center(2) - radius;
w = radius * 2;
h = radius * 2;
pos = [x y w h];
cur = [1 1];
rectangle('Position',pos,'Curvature',cur)
