Draw circle in a rectangular

How to draw a Matlab code that draws a red circle with radius 1 at the center of a green square of sides 20. The square borders should be blue.

Answer 1

[Matt J]

s=([0 0 ; 0 1; 1 1; 1 0]-1/2)*20;

t=linspace(0,360,1000)';
c=[cosd(t), sind(t)];

patch('XData',s(:,1),'YData',s(:,2),'FaceColor','g','EdgeColor','b','LineWidth',3);
patch('XData',c(:,1),'YData',c(:,2),'FaceColor','r','LineStyle','none');
axis equal

[Hussein Haider]

The edges are not blue

[Matt J]

The edges are blue, but the thickness can be increased, which I have now done.

Answer 2

[Matt J]

c=nsidedpoly(1000);
s=subtract(nsidedpoly(4,'Side',20),c);
h=plot([c,s]); axis equal
h(1).FaceColor='red';
h(1).FaceAlpha=1;
h(2).FaceColor='green';
h(2).EdgeColor='blue';

[Hussein Haider]

 Untitled
Undefined function 'nsidedpoly' for input arguments of type 'double'.

Error in Untitled (line 1)
c=nsidedpoly(1000);

[Hussein Haider]

i use MATLAB R2014a

Answer 3

[Matt J]

N=500;

[x,y]=ndgrid(linspace(-10,10,N));

cmsk=x.^2+y.^2>=1; 
emsk=padarray(zeros(N-6),[3,3],1);

[R,G,B]=deal(~cmsk&~emsk,cmsk&~emsk,emsk);
I=cat(3,R,G,B);

imshow(I)

[Hussein Haider]

The edges are not blue

[Matt J]

Now they are.

[Hussein Haider]

thank u