How to create a filled circle?

Hey guys,

I have this function here for drawing circles:

function circles = circle(x,y,r)
hold on
th = 0:pi/50:2*pi;
x_circle = r * cos(th) + x;
y_circle = r * sin(th) + y;
circles = plot(x_circle, y_circle);
hold off

this, however, only draws line circles. What I want to do is draw a filled circle. How do I go about doing this?

Thanks so much!

Answer 1

[Star Strider]

One option is to use the fill (link) function:

function circles = circle(x,y,r,c)
hold on
th = 0:pi/50:2*pi;
x_circle = r * cos(th) + x;
y_circle = r * sin(th) + y;
circles = plot(x_circle, y_circle);
fill(x_circle, y_circle, c)
hold off
axis equal
end

circleout = circle(3, 4, 2, 'g')            % Call ‘circle’ To Create Green Circle

I added a color argument ‘c’ at the end of your current argument list.

Answer 2

[Nakarin Ratsuntia]

This's some simple way to create filled circle with circle equation.

paper = zeros(360,360); %create empty array
[y x] = size(paper); %define y,x as size of array

r = 40; %define radius of a circle

for i=1:y
    for j=1:x
        if ((i-y/2)^2)+((j-x/2)^2)<(r^2);  %define origin is at the center
            paper(i,j) = 1;  %define array inside the circle eq. = 1
        end
    end
end

imshow(paper);  %show image

[Rik]

Why the double loop? You can also do this with an array operation:

%define radius and center coordinates
r=20;x_c=0;y_c=0;

%generate a coordinate grid
[y,x]=ndgrid(-20:20,-50:50);
%perform calculation
paper= (x-x_c).^2+(y-y_c).^2 <= r^2;

%show result
imshow(paper)