Hi lmhall,
The circle should be defined as a function of a vector (small t), not the 2-Dgrid (capital T), so, pleace replace the following lines in your code:
x = r.*cos(T)+a;
y = r.*sin(T)+b;
with:
x = r.*cos(t)+a;
y = r.*sin(t)+b;
and you'll see the line.
Hope it helps,
Edgar
