Plot a circle on a 2D grid

Hi everybody, I would like to plot a circle on a 2D grid. Any advises? Many thanks

Answer 1

[Geoff Hayes]

Please see the MATLAB Wiki entry http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F for several options on drawing circles.

Or you could create three identically sized vectors: the first being the points along the x-axis:

 x = (-r:d:r)';

where r is the radius of the circle and d is the step size. The next vector is just the upper half of the circle according to the equation of the circle:

 cu = sqrt(r^2 - x.^2);

And the third vector is just the lower half of the circle:

 cl = -cu;

You can then apply "shifts" to the data to get the circle centred at coordinate (h,k), and then just plot both halves of the circle.